Release of somatostatin-like immunoreactivity from the perfused canine thyroid. Selective stimulatory effect of calcium ions.

Abstract

A B S T R A C T It is well accepted that the C cells of the thyroid contain somatostatin, but the role in local endocrine function has not yet been firmly established in this organ, and it has not been proved that thyroidal somatostatin is released into the circulation.We have measured the contents of somatostatin-like immunoreactivity in the effluent of canine thyroid glands perfused without recirculation with a synthetic buffer medium. During basal conditions a definite release was consistently found in the order of 10 pg/ml corresponding to 12 pg/min. The somatostatin-like immunoreactivity was studied in dilution experiments and by gel-filtration chromatography, and found to have properties identical to those of synthetic cyclic somatostatin, which was also recovered quantitatively when added to sampling tubes.Various compounds were infused in concentrations that are highly active in pancreas perfusion experiments. 14-min infusion of arginine, 5 and 11.5 mmol/ liter; isoproterenol, 10 The results demonstrate that thyroidal somatostatin is mobilizable, and it appears to be selectively sensitive to calcium stimulation, indicating a possible role in calcitonin release control.