Chronic administration of a gonadotropin-releasing hormone (GnRH) agonist affects testicular microvasculature.

Three months of daily sc injections of adult male dogs with the gonadotropin-releasing hormone agonist (GnRH-A) [D-Trp6, des-Gly-NH2(10)]GnRH ethylamide produced significant decrease in the diameter of seminiferous tubules and conspicuously altered the ultrastructure of testicular microvasculature. In contrast to capillaries and venules in untreated controls, which had typical continuous endothelial layers surrounded by a basal lamina, in testes of dogs chronically treated with GnRH-A, 14.3% of the capillaries and 21.2% of the venules showed wide (30-500 nm) endothelial gaps. In a few capillaries (1.7%) and venules (4%) endothelial fenestrations were found. A high percentage of capillaries (59.3%) and venules (32.8%), with endothelial gaps or continuous endothelium were surrounded by multiple layers of basal lamina. All arterioles, 24.7% of the capillaries and 42.6% of the venules showed the normal features as found in the controls. Superfluous basal laminae, not associated with cells were present in the testes of the chronically treated dogs, but were also found after 4 months of recovery from the GnRH-A treatment. However, within 4 months after cessation of the GnRH-A treatment, the diameters of the seminiferous tubules were comparable to those in untreated controls. Capillaries and venules with endothelial gaps or fenestrations were completely absent. All arterioles, 43.6% of the capillaries and 65.6% of the venules revealed the normal features of continuous endothelium. However, 56.4% of the capillaries and 34.4% of the venules were characterized by superfluous layers of basal lamina.(ABSTRACT TRUNCATED AT 250 WORDS)