Characterization of a pineal-mediated inhibition of pubertal prolactin cell development in blind-anosmic female rats.

The purpose of this study was to define the peripubertal changes in prolactin (PRL) synthesis in blind-anosmic female rats. To do this prepubertal female rats were either rendered blind-anosmic (BA) or blind-anosmic-pinealectomized (BAP) or left intact (INT). Half the animals were killed after 1 wk (before puberty) while the remaining animals were terminated after 4 wk (after puberty). Pituitary PRL synthesis was measured by the in vitro incorporation of 3H-leucine into PRL. Anterior pituitary weight and DNA content did not differ between BA, BAP, and INT animals 1 wk after treatment. There was a 65% increase in weight and a 55% increase in DNA content in INT pituitaries between 1 and 4 wk. While these increases were also present in BAP rats, they were almost entirely prevented in BA animals. PRL synthesis followed a similar pattern with a 78% increase in synthesis in INT groups between 1 and 4 wk which was, once again, almost entirely absent in BA rats. Pinealectomy prevented this effect. Blinding and anosmia in postpubertal animals produced only a minor decrease in PRL synthesis and pituitary weight and no decrease in pituitary cell number. From these data we conclude that the pineal can inhibit the normal proliferation of PRL cells that occurs during puberty in blind-anosmic female rats.