alpha(1)-adrenoceptor subtypes in rat epididymis and the effects of sexual maturation

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Queiroz, DBC [UNIFESP]
Mendes, F. R. [UNIFESP]
Porto, C. S. [UNIFESP]
Avellar, MCW [UNIFESP]
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We have characterized the expression of alpha(1)-adrenoceptor in epididymis from rats in different stages of sexual maturation: 40 (immature), 60 (young adult), and 120 (adult) days of age. Plasma testosterone levels were low in the immature animals but increased significantly in the 60- and 120-day-old animals. These changes were followed by a progressive increase in rat body weight and in caput and cauda epididymis relative weight., Reverse transcription polymerase chain reaction assay indicated that alpha(1a)-, alpha(1b)-, and alpha(1d)-adrenoceptor transcripts were present in both caput and cauda epididymis from adult rats.. Ribonuclease protection assays further indicated that the expression of these alpha(1)-adrenoceptor transcripts differed with age and epididymal region analyzed. Prazosin (nonselective alpha(1) antagonist), 5-methyl urapidil. (alpha(1A)-selective), and BMY 7378 (alpha(1D)-selective) displaced [H-3]prazosin binding curves in caput and cauda epididymis from 40- and 120-day-old rats. the potency order for these antagonists, as calculated from the negative logarithm: of the inhibition constant (pK(i)) values for the high-affinity sites, indicated a predominant population of alpha(1A)-adrenoceptor subtype in caput and cauda epididymis from adult animals. Differences in pK(i) values. in caput and cauda epididymis from immature and adult animals also suggested that the relative amount of alpha(1)-adrenoceptors, at the protein level, is modulated by sexual maturation. Taken together, the changes in alpha(1)-adrenoceptor expression during sexual maturation may suggest specific roles for these receptors in epididymal function.
Biology of Reproduction. Madison: Soc Study Reproduction, v. 66, n. 2, p. 508-515, 2002.