Vasopressin inhibits type-I collagen and albumin gene expression in primary cultures of adult rat hepatocytes.
The mechanisms that regulate collagen gene expression in hepatic cells are poorly understood. Accelerated Ca2+ fluxes are associated with inhibiting collagen synthesis selectively in human fibroblasts (Flaherty, M., and Chojkier, M. (1986) J. Biol. Chem. 261, 12060-12065). In suspension cultures of isolated hepatocytes, the Ca2+ agonist vasopressin increases cytosolic levels of free Ca2+ (Thomas, A.P., Marks, J.S., Coll, K.E., and Williamson, J. R. (1983) J. Biol. Chem. 258, 5716-5725). However, whether vasopressin's interactions with plasma membrane V1 receptors attenuate hepatic collagen production is unknown. We investigated this problem by studying vasopressin's effects on collagen synthesis and Ca2+ efflux in long-term primary cultures of differentiated and proliferation-competent adult rat hepatocytes. Twelve-day-old quiescent cultures were exposed to test substances and labeled with [5-3H]proline. Determinations of radioactivity in collagenase-sensitive and collagenase-resistant proteins were used to calculate the relative levels of collagen production. Synthetic [8-arg]vasopressin stimulated 45Ca2+ efflux within 1 min and inhibited hepatocyte collagen production within 3 h by 50%; overall rates of protein synthesis were not affected significantly. In cultures labeled with [35S]methionine, vasopressin also decreased the levels of newly synthesized and secreted albumin, but not fibrinogen, detected in specific immunoprecipitates analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Northern blot analyses using specific [32P]cDNA probes revealed 70% decreases in hybridizable levels of collagen alpha 1(I) mRNA in hepatocyte cultures treated with either vasopressin or Ca2+ ionophore A23187; hybridizable levels of albumin mRNA also fell approximately 50% following vasopressin treatment. Vasopressin did not affect collagen production in quiescent cultures of mouse Swiss 3T3, human myofibroblast or rat smooth muscle cells; and hepatocyte collagen production was unaffected by treatment with glucagon or dibutyryl cAMP. Thus, accelerated Ca2+ fluxes induced by vasopressin are associated with decreased production of hepatocyte collagen and albumin in primary cultures that simulate quiescent adult rat liver.
Chojkier
M
M
Department of Medicine, Veterans Administration Medical Center, San Diego, California.
Brenner
D A
DA
Leffert
H L
HL
D000375:Aging; D000418:Albumins / Q000096:biosynthesis / Q000235:genetics*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003994:Bucladesine / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002132:Calcium Radioisotopes / Q000378:metabolism; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects*; D005934:Glucagon / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D014667:Vasopressins / Q000494:pharmacology*
D000418:Albumins; D002132:Calcium Radioisotopes; D014667:Vasopressins; D000001:Calcimycin; D003994:Bucladesine; D003094:Collagen; D005934:Glucagon