In Northern analysis, a single mink LH receptor mRNA transcript predominated over two much-weaker bands in mink ovary and testis. This is in contrast with findings in other species including the rat, mouse, human, pig, and sheep, where there are multiple transcripts of varying number, size, and relative abundance. No LH receptor message was detected in the brain or the uterus, as reported in other species. The predominant transcript identified in the mink CL, 2.4 kb, is large enough to encode the entire LH receptor protein, expected to have an open reading frame of approximately 2 kb. Buy Advair Diskus Online
The abundance of LH receptor mRNA in the ovary varied significantly across the preimplantation and early-pos-timplantation stages of mink gestation, in a manner strikingly different from the pattern for prolactin receptor. A transient peak in LH receptor mRNA was present in whole ovaries during the critical period of CL reactivation and directly preceded the preimplantation increase in progesterone production. This provides indirect evidence for a role for LH in the activation of the mink CL. Although no large follicles were found in the ovary after March 21, it remains possible that the peak in LH receptor mRNA is related to a nonluteal ovarian compartment, as LH receptor message did not differ between pooled CL taken on March 21 and March 25, through the critical period of activation. LH involvement in luteal activation is in contrast to observations in previous studies in which prolactin alone induced luteal activation in hypophysectomized mink, indicated by increases in peripheral progesterone concentrations and by successful embryo implantation. Nonetheless, prolactin treatment alone was not capable of maintaining progesterone production and gestation in that study, indicating that one or more other factors are necessary. Determination of whether LH is one of these factors awaits further experimentation.