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  • Author: R. Garcia-Villar x
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M.-P. Laurentie, R. Garcia-Villar, P.-L. Toutain and J. Pelletier

ABSTRACT

The purpose of the present experiment was to characterize LH secretion pulsatility in rams by analysing the instantaneous secretion rate profile obtained by deconvoluting the plasma concentration profile. Plasma LH concentration profiles were obtained by collecting blood samples every 6 min for 24 h during two different sessions separated by an interval of 15 days. Individual kinetic parameters of ovine LH (oLH) were determined following i.v. injection of oLH.

By deconvoluting the plasma concentration profile, it was shown that a pulse has an effective duration of only 20·41±7·69 (s.d.) min whereas the mean duration estimated from measurement of plasma concentrations was 61·00 ± 15·16 min. The number of pulses was similar before and after deconvolution (7·80±1·99 vs 9·70 ± 3·44 pulses/24 h respectively). Using deconvolution the calculated production rate was 2·26 ± 0·94 μg/kg per 24 h, about 50% of this production being located in the pulses. Statistical analysis of pulsatility revealed that pulse occurrence was a non-periodic event and that the amplitude of LH pulses and the associated amount of LH released were correlated with the duration of the preceding quiescence period, but had no statistically significant influence on the duration of the following quiescence period.

Journal of Endocrinology (1992) 133, 75–85

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R. Garcia-Villar, D. Schams, M. Alvinerie, M. P. Laurentie and P. L. Toutain

ABSTRACT

Experiments were conducted in the ewe to determine the effects of mating on the activity of the genital tract and on blood levels of oxytocin and cortisol. The activity of the uterus and cervix was recorded by electromyography, oxytocin was measured by radioimmunoassay, and cortisol by high performance liquid chromatography. Mating itself did not increase circulating oxytocin or cortisol; uterine motility remained unchanged during and after copulation but the cervix was significantly stimulated during teasing and after copulation. It is suggested that increased cervical activity resulting from adrenergic mechanisms may facilitate the generation of a cervical reserve of spermatozoa.

J. Endocr. (1985) 105, 323–329

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A. Vass-Lopez, R. Garcia-Villar, M. Lafontan and P. L. Toutain

ABSTRACT

The adrenergic antagonists [3H]prazosin and [3H] rauwolscine were used to identify α1- and α2-adrenoceptors respectively in the ovine myometrium. Ewes were allocated to four groups according to steroid hormone treatments or physiological status, namely ovariectomized ewes either as untreated controls, treated with oestradiol-17β or progestagen plus oestradiol-17β, and pregnant ewes at mid-gestation. Binding of both [3H]prazosin and [3H]rauwolscine to membrane preparations from the ovine myometrium was saturable, of high affinity and rapidly reversed by phentolamine (10 μmol/l). Based on the relative order of potency of selected adrenergic agonists and antagonists, the myometrial binding sites labelled by [3H]prazosin and [3H]rauwolscine were characterized as α1- and α2adrenoceptors respectively. Saturation binding studies with [3H]prazosin showed that the number of α1adrenoceptors was low (maximal binding capacity, Bmax, between 19 and 24 fmol/mg protein) and there were no noticeable differences between the animal groups. Moreover, the equilibrium dissociation constant (K d) did not vary significantly between groups (K d between 0·10 and 0·17 nmol/l). In contrast, saturation binding studies with [3H]rauwolscine revealed the presence of a high number of α2-adrenoceptors. Values of Bmax were far higher in the pregnant ewes (1096±241 fmol/mg protein; means ± s.d.) than in any of the non-pregnant ovariectomized ewes. For these latter groups, the highest Bmax values were found in the group treated with both progestagen and oestrogen (382±77 fmol/mg protein) compared with treatment with oestrogen alone (101±8 fmol/mg protein) or with controls (82±12 fmol/mg protein). The results of the present study, especially those obtained under a high-progesterone environment (e.g. pregnancy), strongly suggest a role of steroid hormones in the control of the number of α2-adrenoceptors in the ovine myometrium. In contrast, they did not yield any supporting data for a similar role on myometrial α1-adrenoceptors in the ewe.

Journal of Endocrinology (1990) 127, 471–479