Effect of portacaval anastomosis and chronic underfeeding on the hypothalamic-pituitary-gonadal axis in the rat.

Portacaval anastomosis (PCA) in the rat may be a useful experimental model for examining endocrine changes that occur during cirrhosis of the liver. A marked reduction in diet intake and body weight occurs in rats after establishing the shunt and studies were undertaken to determine the relationship of these effects to the testicular atrophy that also follows PCA. Control, sham-operated animals, experiencing a reduction in food intake similar to that of the animals with a PCA, showed reduced plasma levels of LH and testosterone but also exhibited a marked testicular response to LH. This was consistent with increased sensitivity of the hypothalamic-pituitary axis to the negative feedback of gonadal steroids in chronically underfed animals. Male rats with a PCA exhibited similarly reduced levels of LH and testosterone, but showed poor secretory responses of the pituitary gland to LH releasing hormone (LH-RH) and of the testis to LH. Testicular atrophy and cessation of spermatogenesis occurred in the animals with a PCA. These results suggested that the effects of PCA on the pituitary-gonadal axis cannot simply be explained as a consequence of the restricted intake of diet. This was confirmed by the responses to castration. In both fed and underfed sham-operated rats, castration resulted in a rapid and sustained increase in plasma LH and both groups showed a marked LH secretory response to LH-RH. In contrast, in animals with a PCA castration had little effect on plasma LH and the pituitary response to LH-RH was still poor. The effects of PCA cannot be simply explained by impeded metabolism of gonadal steroids causing increased negative feedback on the hypothalamic-pituitary axis.