Role of steroids in secretion—modulating effect of triamcinolone and estradiol on protein synthesis and secretion from the rat exocrine pancreas

Following adrenalectomy of male rats, or adrenalectomy and ovariectomy of females, there was marked depletion of zymogen granules in acinar cells of the pancreas. Within 9 h after treatment with either triamcinolone or 17β-estradiol, complete restoration of these secretory vesicles was observed. This repletion was not inhibited by actinomycin-D. Supernatant fractions (100,000 g, 60min) of rat pancreas, from both normal and surgically altered animals, contained proteins that bound [ 3H]-triamcinolone and [ 3H]-estradiol, suggesting that the action of these hormones is exerted directly on the pancreas. Binding of both steroid hormones required the presence of an additional coligand referred to as accessory factor. In addition, the binding proteins for [ 3H]-triamcinolone and [ 3H]-estradiol eluted in similar positions after Sephadex G-200 and CM Affi-gel Blue chromatography. It is uncertain, however, whether a single protein binds both steroid hormones since they had different binding isotherms. Scatchard analysis of binding of [ 3H]-estradiol yielded a single straight line of negative slope from which it was calculated that there were about 4.4 pmol of binding sites per mg protein, having an average apparent K d of about 5 × 10 −8M. Similar analysis of the data for [ 3H]-triamcinolone yielded a straight line of zero slope indicating nonsaturable binding of hormone at concentrations as high as 10μM. Since both [ 14C]- L-leucine incorporation into protein and amylase secretion were affected markedly by the steroid-hormonal status of the animal, it is presumed that steroid-bound complexes in acinar cells of the pancreas modulate synthesis and secretion of protein.