Prolactin and Lutenizing hormone levels during diestrus and proestrus in mice

Prolactin secretion patterns are species-specific, variable and influenced
by multiple factors including circadian and hormonal cues, stress,
physiological state and reproductive strategy. In nonpregnant females,
circulating prolactin levels are low; however, during the afternoon of
proestrus an estradiol-induced prolactin surge coinciding with the
preovulatory LH surge has been recorded in many (but not all) species. In
mice, there have been conflicting reports relating to the occurrence and
timing of this surge. To gain insight into the characteristics of
circulating prolactin levels during proestrus we have used repeated tail
tip blood sampling in C57BL/6J and Swiss Webster mice to profile prolactin
secretion in individual mice. For this study we have measured prolactin
levels during diestrus and proestrus using an ultra-sensitive prolactin
ELISA. To establish the relationship between circulating prolactin levels
and the timing of the LH surge we have simultaneously measured LH levels
in the same samples via ELISA. In mice circulating prolactin levels in
proestrus do not follow a classical surge pattern but show prolonged
elevation which is not tightly linked to the light/dark cycle.