AJP - Endocrinology and Metabolism, Vol 258, Issue 4 E661-E666, Copyright © 1990 by American Physiological Society
In vivo somatostatin, vasopressin, and oxytocin synthesis in diabetic rat hypothalamus
J. D. Fernstrom, M. H. Fernstrom and R. P. Kwok
Department of Psychiatry, University of Pittsburgh School of Medicine, Pennsylvania 15213.
The in vivo labeling of somatostatin-14, somatostatin-28, arginine
vasopressin, and oxytocin was studied in rat hypothalamus after third
ventricular administration of [35S]cysteine to streptozotocin-diabetic and
normal rats. Immunoreactive somatostatin levels in hypothalamus were
unaffected by diabetes, as was the incorporation of [35S]cysteine into
hypothalamic somatostatin-14 and somatostatin-28. In contrast,
immunoreactive vasopressin levels in hypothalamus and posterior pituitary
(and oxytocin levels in posterior pituitary) were below normal in diabetic
rats. Moreover, [35S]cysteine incorporation into hypothalamic vasopressin
and oxytocin (probably mainly in the paraventricular nucleus because of its
proximity to the third ventricular site of label injection) was
significantly above normal. The increments in vasopressin and oxytocin
labeling were reversed by insulin administration. In vivo cysteine specific
activity and the labeling of acid-precipitable protein did not differ
between normal and diabetic animals; effects of diabetes on vasopressin and
oxytocin labeling were therefore not caused by simple differences in
cysteine specific activity. These results suggest that diabetes 1) does not
influence the production of somatostatin peptides in hypothalamus but 2)
stimulates the synthesis of vasopressin and oxytocin. For vasopressin at
least, the increase in synthesis may be a compensatory response to the
known increase in its secretion that occurs in uncontrolled diabetes.
