Gonadotropin-induced changes in oviducal mRNA expression levels of sex steroid hormone receptors and activin-related signaling factors in the alligator

Abstract

Oviducts respond to hormonal cues from ovaries with tissue proliferation and differentiation in preparation of transporting and fostering gametes. These responses produce oviducal microenvironments conducive to reproductive success. Here we investigated changes in circulating plasma sex steroid hormones concentrations and ovarian and oviducal mRNA expression to an in vivo gonadotropin (FSH) challenge in sexually immature, five-month-old alligators. Further, we investigated differences in these observed responses between alligators hatched from eggs collected at a heavily-polluted (Lake Apopka, FL) and minimally-polluted (Lake Woodruff, FL) site. In oviducts, we measured mRNA expression of estrogen, progesterone, and androgen receptors and also beta A and B subunits which homo- or heterodimerize to produce the transforming growth factor activin. In comparison, minimal inhibin alpha subunit mRNA expression suggests that these oviducts produce a primarily activin-dominated signaling milieu. Ovaries responded to a five-day FSH challenge with increased expression of steroidogenic enzyme mRNA which was concomitant with increased circulating sex steroid hormone concentrations. Oviducts in the FSH-challenged Lake Woodruff alligators increased mRNA expression of progesterone and androgen receptors, proliferating cell nuclear antigen, and the activin signaling antagonist follistatin. In contrast, Lake Apopka alligators displayed a diminished increase in ovarian CYP19A1 aromatase expression and no increase in oviducal AR expression, as compared to those observed in Lake Woodruff alligators. These results demonstrate that five-month-old female alligators display an endocrine-responsive ovarian-oviducal axis and environmental pollution exposure may alter these physiological responses.

Expression of leptin receptor in the oviduct of Chinese brown frog (Rana dybowskii)

“…The female reproductive tract exhibits alterations in structure and function developmentally as well as with seasonal reproductive activity (25). In this study, morphological differences of oviduct in the breeding and prehibernation period were investigated, revealing seasonal changes in weight and circumference with distinct differences, namely the significant increase in oviductal weight and diameter during prehibernation rather than during the breeding period.…”

Expression of cocaine- and amphetamine-regulated transcript (CART) in hen ovary

“…The inhibitory actions of CART on FSH signaling and E 2 production depend on the Go/i-subclass of inhibitory G proteins and are linked to multiple components of the FSH signal transduction pathway, resulting in reduced CYP19A1 mRNA and E 2 production [ 11 , 14 ]. CYP19A1 is the steroidogenic enzymes responsible for androgen synthesis and the aromatization of androgens to estrogens [ 21 ]. In immature chicken ovaries, exogenous FSH induces steroidogenesis by increasing CYP19A1 mRNA expression and subsequent progesterone synthesis [ 22 ].…”

Ecotoxicological Risk of Endocrine Disruptors

“…Environmental exposure to anthropogenic contaminants alters the development and functioning of American alligators' reproductive and endocrine systems (Milnes and Guillette, 2008;Woodward et al, 2011;Moore et al, 2012). Thus, repeated episodes of Nile crocodile deaths have been suspected to be due to similar dysfunctioning.…”