Peripheral vascular effects of opioid peptides are well known, but direct myocardial effects have not been established. We studied the inotropic response of spontaneously beating cultured chick embryo ventricular cells to the enkephalin analogue [D-Ala2]-enkephalin. Amplitude of cell motion increased in a concentration-dependent manner with 0.53 microM [D-Ala2]-enkephalin producing half-maximal response. The mechanism of this positive inotropic effect was investigated by examining alterations in 45Ca influx, cyclic AMP accumulation and adenylate cyclase activity in response to [D-Ala2]-enkephalin. At maximally inotropic concentrations, the 45Ca influx rate increased 39%, adenylate cyclase was stimulated by 30%, and cyclic AMP content rose more than twofold. Thus, in contrast to neural tissue, receptors for enkephalin in cultured heart cells are coupled to adenylate cyclase in a stimulatory manner. Occupancy of these receptors produces an increase in cyclic AMP levels and exerts a positive inotropic effect via a verapamil-sensitive enhancement of Ca influx.
S Laurent, J D Marsh, T W Smith
As the characteristics of sodium and water balance in heart failure remain undefined, we evaluated the hemodynamic, metabolic, and hormonal effects of balanced sodium intake in 10 patients with chronic congestive heart failure. We discontinued diuretics to avoid their confounding influence, and all patients received 1 wk of 10 meq and 100 meq balanced sodium intake and controlled free water. Comparing sodium intake of 10 with 100 meq, the following observations were made. There was weight gain (2.0 kg) and increased sodium excretion (11 +/- 3 to 63 +/- 15 meq/24 h), unaccompanied by increase of blood volume. Both renin-angiotensin system and sympathetic nervous system activity were greater during the 10 meq diet, and suppressed with the 100 meq sodium diet. For both diets, plasma renin and urinary aldosterone excretion were correlated with urinary sodium excretion (r = -0.768, r = -0.726, respectively; P less than 0.005). Systemic hemodynamics were minimally changed with increased sodium intake. However, reversal of vasoconstriction by captopril during the 10 meq diet, and its ineffectiveness during the 100 meq diet, indicated a renin-dependent mechanism in the former, and a renin-independent mechanism in the latter diet. There were two subgroups of response to the 100 meq diet: one group (n = 5) achieved neutral balance, while the second (n = 5) avidly retained sodium and water. Renin-angiotensin system activity was significantly higher in the latter group, and the mechanism for differences in sodium excretion for the subgroups could not be identified by blood volume or hemodynamic parameters. Orthostatic hypotension during tilt was greater during the 10 meq sodium diet, and in all cases, related to ineffective hemodynamic and hormonal compensatory responses.
R J Cody, A B Covit, G L Schaer, J H Laragh, J E Sealey, J Feldschuh
Effects of intraperitoneal injection of allogeneic lymphocytes on insulin secretion were studied in incubated pancreas slices from BALB/c mice. Injection of allogeneic lymphocytes from C57BL/6J (H2b) mice increased insulin secretion, both in basal and 11-mM glucose-stimulated conditions. This effect was only present when at least 5 X 10(6) or 1 X 10(6) cells were injected (in basal and stimulated conditions, respectively). Glucose-induced insulin secretion (3.3-27.5 mM) was significantly increased in pancreata from mice injected with allogeneic lymphocytes. No effect was observed when glucose was not included in the incubation medium. Intraperitoneal injection of Dextran 70 produced no change in glucose-elicited insulin secretion. There were no differences in glucagon and somatostatin (SRIF) secretion obtained from pancreas of mice injected with allogeneic or syngeneic lymphocytes. Injection of allogeneic cells increases insulin secretion (basal and both phases of 11 mM glucose-stimulated secretion). Puromycin significantly inhibited the second phase of insulin secretion. These results suggest that: Injection of allogeneic lymphocytes raises both basal and glucose-stimulated insulin secretion. This effect seems to be connected with the major histocompatibility complex, and to be related to the number of allogeneic cells injected. Injection of allogeneic lymphocytes seems to sensitize the beta cell response to glucose stimulus. Neither glucagon nor SRIF secretion are altered by alloantigen injection. The stimulatory effect of allogeneic lymphocytes is related, at least in part, to insulin synthesis.
J B García, M C Venturino, E Alvarez, L Fabiano de Bruno, M Braun, O H Pivetta, J C Basabe
Cholesterol-rich very low density lipoproteins (VLDL) from the homozygous Watanabe heritable hyperlipidemic (WHHL) rabbit induced marked cholesteryl ester accumulation in mouse peritoneal macrophages. This WHHL rabbit, an animal model of human familial hypercholesterolemia, has severe hypercholesterolemia, cutaneous xanthomas, and fulminant atherosclerosis due to the deficiency of the low density lipoprotein (LDL) receptor. When incubated with mouse peritoneal macrophages, the VLDL from WHHL rabbit (WHHL-VLDL) stimulated cholesteryl [14C]oleate synthesis 124-fold more than did VLDL from the normal Japanese White rabbit (control-VLDL). The enhancement in cholesteryl ester synthesis and accumulation of WHHL-VLDL was due to the presence of a high affinity binding receptor site on the macrophage cell surface that mediated the uptake and lysosomal degradation of WHHL-VLDL. Competition studies showed that the uptake and degradation of 125I-WHHL-VLDL was inhibited by unlabeled excess WHHL-VLDL and beta-migrating VLDL (beta-VLDL), but not LDL. Furthermore, the degradation of WHHL-VLDL was not blocked by either fucoidin, polyinosinic acid, or polyguanylic acid, potent inhibitors of the acetylated (acetyl)-LDL binding site, or by acetyl-LDL. These results suggest that macrophages possess a high affinity receptor that recognizes the cholesterol-rich VLDL present in the plasma of the WHHL rabbit and that the receptor which mediates ingestion of WHHL-VLDL seems to be the same as that for beta-VLDL and leads to cholesteryl ester deposition within macrophages. Thus the uptake of the cholesterol-rich VLDL from the WHHL rabbit by macrophages in vivo may play a significant role in the pathogenesis of atherosclerosis in the WHHL rabbit.
T Kita, M Yokode, Y Watanabe, S Narumiya, C Kawai
HTLV-I is a transforming human retrovirus that is an etiologic agent of adult T cell leukemia/lymphoma. To investigate the effects of this virus on T cell functions, two OKT3+, OKT4+, OKT8- cytotoxic clones (8.7 and 8.8) specific for allogeneic cells bearing DPw2, a class II histocompatibility antigen, were studied before and after infection with HTLV-I. The clones retained cytotoxic function for up to 70 d after exposure to HTLV-I, even without subsequent antigenic stimulation, but then lost their cytotoxic activity. Prior to infection with HTLV-I, clone 8.8 also lysed OKT3 hybridoma cells; after infection, cytotoxic activity against these OKT3-antibody bearing cells was lost in parallel with the loss of activity against DPw2-bearing target cells. In addition, expression of T3 surface antigen by HTLV-I-infected 8.8 cells was decreased at a time when they lost their cytotoxic activity, possibly contributing to the loss of cytotoxic function. Finally, clone 8.8 could provide help for nonspecific IgG production by autologous B cells when stimulated with irradiated DPw2-bearing non-T cells. After infection with HTLV-I, this helper function became independent of DPw2-stimulation and persisted even when the cytotoxic activity was lost. An OKT4+ T cell clone thus could simultaneously manifest both cytotoxic and helper T cell activities, and these activities were differentially affected after HTLV-I infection.
R Yarchoan, H G Guo, M Reitz Jr, A Maluish, H Mitsuya, S Broder
In this study, carried out in the rat and hamster, the receptor-dependent low density lipoprotein (LDL) transport process in each organ was characterized in terms of its maximal uptake rate (Jm) and Michaelis constant (Km), while the rate of receptor-independent uptake was defined in terms of its proportionality constant (P). The highest Jm values of 50-126 micrograms/h per g were found in the liver and endocrine glands in both species and receptor-dependent uptake also was detected in other organs like spleen, kidney, and intestine. The Km values were essentially the same in all of the organs and equaled approximately 90 mg/dl in both species. The receptor-independent uptake constants also were similar in the two species and were highest in the spleen, liver, and intestine. From these values for Jm, Km, and P, it was possible to construct theoretical curves that predict the plasma LDL-cholesterol concentration and fractional catabolic rate given any alteration in LDL-cholesterol production or the magnitude of receptor-dependent LDL transport in any organ of the rat or hamster.
D K Spady, J B Meddings, J M Dietschy
The development of atherosclerotic changes and thromboembolism are common features in homocystinurics. Hence, we postulate a positive correlation between the level of homocyst(e)ine in the blood and the occurrence of coronary artery disease. Homocysteine is found either as free homocystine, cysteine-homocysteine mixed disulfide, or protein-bound homocyst(e)ine. In nonhomocystinuric subjects, most homocysteine molecules are detectable in the protein-bound form. Thus, protein-bound homocyst(e)ine in stored plasma which reflected total plasma homocyst(e)ine was determined in 241 patients with coronary artery disease (173 males and 68 females). The mean +/- SD total plasma homocyst(e)ine was 5.41 +/- 1.62 nmol/ml in male patients, 4.37 +/- 1.09 nmol/ml in male controls, 5.66 +/- 1.93 nmol/ml in female patients, and 4.16 +/- 1.62 nmol/ml in female controls. The differences between the patients with coronary artery disease and the controls were statistically significant (P less than 0.0005).
S S Kang, P W Wong, H Y Cook, M Norusis, J V Messer
We made longitudinal measurements of bone mineral density (BMD) in 139 normal women (ages 20-88 yr) at midradius (99% cortical bone) and lumbar spine (approximately 70% trabecular bone) by single- and dual-photon absorptiometry. BMD was measured 2-6 (median, 3) times over an interval of 0.8-3.4 yr (median, 2.1 yr). For midradius, BMD did not change (+0.48%/yr, NS) before menopause but decreased (-1.01%/yr, P less than 0.001) after menopause. For lumbar spine, there was significant bone loss both before (-1.32%/yr, P less than 0.001) and after (-0.97%/yr, P = 0.006) menopause; these rates did not differ significantly from each other. Our data show that before menopause little, if any, bone is lost from the appendicular skeleton but substantial amounts are lost from the axial skeleton. Thus, factors in addition to estrogen deficiency must contribute to pathogenesis of involutional osteoporosis in women because about half of overall vertebral bone loss occurs premenopausally.
B L Riggs, H W Wahner, L J Melton 3rd, L S Richelson, H L Judd, K P Offord
The kinetics of entry and release of gentamicin was investigated in fluids and tissues of the inner ear of the rat, as well as in renal cortex, and in organs that do not share susceptibility to the toxic effects of aminoglycosides. Various modes of administration were used to achieve different patterns of drug plasma concentrations. Electrophysiological and histological examinations were performed to correlate pharmacokinetics and ototoxicity. Results show that: the uptake of the drug by the inner ear tissues is dose dependent and manifests a rapid saturation kinetics with a concentration plateau of about 1 micrograms/mg of protein. The low ratio of the perilymph and endolymph to plasma concentrations argues against the concept of an accumulation of the drug in the inner ear over drug levels in plasma, which has been considered as the basic mechanism of ototoxicity. In renal cortex, the kinetics appears similar to that of the inner ear but the concentrations achieved are 10-fold higher than in cochlear tissues. In other organs (liver, heart, lung, and spleen), no saturation could be demonstrated within the duration of the experiment. Ototoxicity seems to be related to the penetration of the drug into compartment(s) from which the half-life of disappearance is extremely slow. Rapid uptake, early saturation, and long exposure of the tissues to the drug may account for the development of toxicity in inner ear and kidney.
P Tran Ba Huy, P Bernard, J Schacht
Different T cell lines, which can be induced to secrete interleukin 2 (IL-2) in vitro, were used to dissect the effect of cyclosporin A (CsA). The T leukemia cell Jurkat requires an increase in cytoplasmic calcium concentration ([Ca++]i) and phorbol myristate acetate (PMA) for the induction of IL-2 production, which is completely blocked by CsA. Another T cell line, HUT 78, also produces IL-2 in response to a rise in [Ca++]i and PMA; however, in HUT 78, PMA alone induces low levels of IL-2 production that is not blocked by CsA. After treatment with 5-azacytidine, HUT 78 cells produced maximal levels of IL-2 in response to PMA alone without requiring [Ca++]i increasing stimuli. In these cells no inhibitory effect of CsA on PMA-induced activation could be demonstrated. In addition, CsA does not inhibit PMA-induced translocation of protein kinase C. These data suggest that CsA does not globally inhibit IL-2 gene expression, but rather interferes with signaling events of T cell activation.
B Manger, K J Hardy, A Weiss, J D Stobo