THE EFFECT OF SOMATOSTATIN ANALOG OCTREOTIDE ON DIETHYLSTILBESTROL-INDUCED PROLACTIN SECRETION, CELL-PROLIFERATION AND VASCULAR CHANGES IN THE RAT ANTERIOR-PITUITARY GLAND

The effects of diethylstilbestrol (DES) and of long-acting somatostati n analog, octreotide (SMS) on the rat anterior pituitary microvasculat ure have been studied by means of computer-assisted image analysis. Ad ditionally, the effects of DES and SMS on prolactin secretion and ante rior pituitary cell proliferation have been studied, as well. The vasc ularization was visualized using Selye's method modified by Poely et a l. (1964). The prolactin serum levels were estimated by radioimmunoass ay. The proliferation indices were assessed using bromodeoxyuridine in corporation assay. As expected, it was found that DES sharply increase d serum prolactin levels and enhanced cell proliferation in the anteri or pituitary gland. DES also induced changes in parameters of vascular ization. Simultaneous treatment of rats with SMS inhibited the DES-ind uced elevation of prolactin levels and pituitary cell proliferation. I t also suppressed some but not all DES-induced changes in the anterior pituitary vascularization. These data suggest that the angio-inhibito ry activity of SMS might be involved in its anti-tumor action on pitui tary adenomas, but not as a sole or principal mechanism.