ABSTRACT
Prostaglandin (PG) E2 and F2 alpha synthesis by isolated glomeruli and papillary homogenates prepared from control, salt-loaded, and salt-depleted rats was measured in vitro with and without added arachidonic acid using specific radioimmunoassays. Glomeruli from salt-depleted rats synthesized less PGE2 and more PGF2 alpha than glomeruli from control rats under both conditions. The effect of sodium restriction could be attributed to stimulation of glomerular 9-keto-PGE2 reductase activity unrelated to a change in the concentration of this enzyme. High salt diet had no effect on PG synthesis by glomeruli. Papillary homogenates prepared from salt-loaded rats synthesized more PGE2 than those from control rats both with and without added arachidonic acid. This finding suggests an effect of high salt diet at a stage further than phospholipid deacylation. Low salt diet had no effect on PG synthesis by papillary homogenates. The physiological control of PG synthesis in response to changes in the NaCl content of the diet is, therefore, different for the glomeruli and the papilla.
Subject(s)
Kidney Glomerulus/metabolism , Kidney/metabolism , Prostaglandins E/biosynthesis , Prostaglandins F/biosynthesis , Sodium/pharmacology , Animals , Arachidonic Acid , Arachidonic Acids/pharmacology , Dinoprost , Dinoprostone , In Vitro Techniques , Kidney/drug effects , Kidney Glomerulus/drug effects , Kinetics , Rats , Rats, Inbred StrainsABSTRACT
Tritiated salmon calcitonin was prepared by methylation of the free amino groups using tritiated sodium borohydride as precursor. Specific radioactivity was measured in competitive inhibition studies with specific anticalcitonin antibodies or tubular membranes as binding sites for calcitonin. The value observed, approx. 4 Ci/mmol, corresponded to methylation of one third of the available N-H bonds. Tritiated calcitonin prepared in this way retained full biological activity as assessed in vitro by stimulation of adenylate cyclase and in vivo by rat bioassay. Tritiated calcitonin specifically bound to isolated renal cells and nonspecific binding did not exceed 10% of total binding. Equilibrium was obtained after 15 min incubation. The hormone-receptor complex could be dissociated in the presence of an excess of unlabelled calcitonin. This data shows that tritiated calcitonin can be used in metabolic and receptor studies.
