@entity398 modulates the luteinizing hormone response of the XXXX anterior pituitary to gonadotrophin-releasing hormone in vitro.

@entity398 @entity35 @entity1176
Although @entity1176 is believed to be the primary secretagogue for LH, @entity398 has also been shown to stimulate LH release from the anterior pituitary. We investigated the possibility that the two secretagogues interact in the modulation of LH release. Anterior pituitaries were removed from adult female @entity35 at pro-oestrus, and tissue pieces were pre-incubated in @entity398 for 3 h prior to being stimulated with 15 min pulses of @entity1176 . LH output over the 1 h period from the beginning of the @entity1176 pulse was determined. Control incubations were carried out in the absence of @entity398 , and background secretory activities without @entity1176 stimulation were also determined. Tissue which was pre-exposed to @entity398 (0.012-1.25 microM) had an increased LH response to @entity1176 (1.25 nM). The increase was larger than the sum of the LH outputs obtained with @entity398 and @entity1176 separately, revealing that @entity398 synergistically enhanced LH secretion elicited by @entity1176 (P < 0.05; ANOVA). If stimulation by @entity1176 was delayed for 2 h after incubation with @entity398 , an increase in LH secretion was still observed, indicating that @entity398 -induced modulation did not rapidly disappear. @entity398 pre-incubation was observed to result in an increase of maximal @entity1176 -induced LH output (P < 0.001; t-test), as well as an increase of intermediate responses. The LH response of the anterior pituitary to subsequent pulses of @entity1176 was modified by the self-priming process. The effect of @entity398 pretreatment on the response of primed tissue to @entity1176 was also investigated.(ABSTRACT TRUNCATED AT 250 WORDS)
