PMID: 8585662Nov 1, 1995Paper

Down-regulation of beta-adrenergic receptors and up-regulation of estrogen and progesterone receptors induced in the reproductive system of female veal calves by dietary clenbuterol

American Journal of Veterinary Research
G ReCarlo Girardi

Abstract

Effects induced by long-term administration of clenbuterol at anabolic dosages (20 micrograms/kg of body weight for 40 days) on beta-adrenergic receptor (beta-AR) subtypes, estrogen receptors (ER), and progesterone receptors (PgR) in the reproductive system of female veal calves were investigated. Clenbuterol treatment induced a significant (P < 0.01) down-regulation of beta-AR subtypes (beta 1-AR, beta 2-AR, myometrial high-affinity beta 2-AR, and ovarian low-affinity beta 2-AR). On the other hand, a significant (P < 0.01) increase of uterine and ovarian ER and PgR receptors was observed in treated calves. Treatment did not affect dissociation constant values of beta-AR, ER, or PgR. In similar manner, clenbuterol did not significantly modify distribution of ER and PgR in the various tissues of the genital tract. In fact, these receptors were significantly (P < 0.05) more concentrated in the uterus than in the vagina in treated and untreated calves. Data indicated that prolonged clenbuterol exposure induced homologous beta-AR down-regulation (down-regulation of its specific receptors) and heterologous ER and PgR up-regulation (up-regulation of different types of receptors, not specifically bound by clenbuterol) in the genital t...Continue Reading

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