Cellular localization and changes in expression of prolactin receptor isoforms in sheep ovary throughout the estrous cycle

Abstract

The actions of prolactin (PRL) on target cells depend on the type of prolactin receptor (PRLr) predominantly expressed, particularly whether the long PRLr isoform is expressed. The aims of this study were to determine the cellular localization and the changes in expression of long and short PRLr isoforms in sheep ovary throughout the estrous cycle. Long and short PRLrs were localized mostly in the same ovarian cells. Maximum signal intensity, particularly for long PRLrs, was found in stromal cells surrounding primordial and primary follicles, and, for both PRLrs, in granulosa cells of preantral follicles and in luteal cells. Moderate signal intensity for PRLrs was found in theca cells of preantral to ovulatory follicles, and in granulosa cells of antral follicles up to the gonadotropin-dependent stage. Decreasing immunoreactivity to PRLrs was found in granulosa cells of gonadotropin-dependent to ovulatory follicles. For long PRLrs in particular, no signal was found in mural granulosa cells of gonadotropin-dependent follicles; for both isoforms, no signal was found in most granulosa cells of ovulatory follicles. In primordial to gonadotropin-dependent follicles, cellular localization of PRLr was similar on days 0, 10 and 15 of the cycle. Oocytes consistently showed positive immunostaining for PRLrs. Comparative RT-PCR analysis of long and short PRLr expression showed that the short isoform is evenly expressed throughout the estrous cycle, whereas the expression of the long form increases at the time of estrus and decreases at mid-luteal phase and at the onset of the follicular phase. Expression of long PRLrs was greater than that of short PRLrs on day 0 of cycle; expression of both isoforms was similar on day 10 and on day 15, long PRLrs expression was lower than that of short PRLrs. Our results indicate that in sheep ovary, the maximum responsiveness to PRL might occur during the preovulatory phase of the estrous cycle.

Seasonal Endocrine Changes and Breeding Activity in Mediterranean Wild Ruminants

“…Prolactin is a modulator of cell proliferation and differentiation, whereby it might play a role in ovarian follicular growth. Indeed, it has been documented by the existence of changes in the expression of prolactin receptor isoforms throughout the oestrous cycle in sheep ovary (Picazo et al. 2004).…”

Global gene expression in the bovine corpus luteum is altered after stimulatory and superovulatory treatments

“…The PRLRS and PRLRL mRNA and protein levels were upregulated in stimulated animals, whereas only the PRLRS protein was increased in superovulated animals. These results point towards a possible role of eCG in the regulation of PRLR expression and they suggest that the expression of each PRLR isoform can be regulated independently (Picazo et al 2004). Furthermore, the increase in PRLRS expression in superovulated animals could be related to its action on cell proliferation and angiogenesis (Bole-Feysot et al 1998;Stocco 2012), whereas the increase of PRLRL in stimulated animals could be related to prolactin's effect on luteal progesterone production (Stocco 2012).…”

The expression of prolactin and its cathepsin D-mediated cleavage in the bovine corpus luteum vary with the estrous cycle

“…In contrast, PRL signaling appears not to affect all of these processes in ruminants (8) and primates (68), although all of the PRL-receptor forms described to date are expressed in the gland (64,70,74).…”