Biomedical subjects

G Castex

Publications and source records attributed to G Castex.

3 recordsLinked to original sources

PubMed2003

Secretory patterns of prolactin in dogs: circannual and ultradian rhythms.

The objectives of the present study were to characterize in dogs circannual and ultradian prolactin (PRL) secretory patterns and also to compare gender differences in the ultradian period of study in the Southern hemisphere. Blood samples were collected at 15-min intervals for 2.5 h from seven male and seven female dogs and a single monthly sampling, over a 1-year time span, from six male dogs for the ultradian and circannual studies, respectively. Plasma PRL was measured by a homologous enzyme immunometric assay. The ultradian study evidenced PRL elevations suggesting pulsatile secretion in both genders. Significantly higher mean smoothed baseline (ng / ml [7.02 +/- 1.2 vs 1.23 +/- 1.0, p < 0.01]) and AUC (ng/ml * 2.5 h [25.2 +/- 3.8 vs 4.4 +/- 3.8, p < 0.01]) were found in females when compared with males. In the circannual study, plasma PRL concentrations did not statistically differ among the months of the year. When grouped together the 3 months with a longer daylight had significantly higher PRL concentrations than the 3 months with the shortest (2.31 +/- 0.37 vs 0.96 +/- 0.37, p < 0.01). The correlation between length of daylight and PRL concentrations was 0.24, p < 0.05. It is concluded that PRL does have a circannual rhythmicity and that there are ultradian gender-related differences in the period under study in these groups of dogs. This study also demonstrates plasma PRL elevations suggesting pulsatile secretion in male dogs.

Animals↗

PubMed2003

Coat colour changes associated with cabergoline administration in bitches.

Cabergoline or bromocriptine were administered orally to 60 bitches at doses of 5 microg/kg and 15 microg/kg daily, respectively, for two to 45 days for the treatment of pseudopregnancy or for oestrus induction. Seven of the dogs which received cabergoline for more than 14 days developed coat colour changes from the second week of administration to the next coat shedding. Of these, fawn-coloured bitches developed a yellowish coat colour while Argentine boar hounds became black spotted, mainly on their extremities. In previous untreated oestrous periods, these bitches had shown no coat colour changes. It is concluded that a colour shift in certain haircoats of particular breeds could be mediated through the inhibition of the secretion of melanocyte-stimulating hormone by the administration of the dopaminergic agonist cabergoline for more than two weeks. Transient coat colour changes should be considered a possible side effect when planning long-term treatment with dopaminergic agonists in dogs.

Animals↗

PubMed2001

Dioestrous ovariectomy: a model to study the role of progesterone in the onset of canine pseudopregnancy.

It has been suggested that overt pseudopregnancy in bitches is caused by an increase in the concentration of serum prolactin as a result of an abrupt decrease in progesterone concentration in the late luteal phase. This hypothesis was tested by using ovariectomy at dioestrus as an experimental model. A total of 18 intact cross- and purebred bitches were used. Eleven animals were ovariectomized (day 0) between day 25 and day 40 of the oestrous cycle, and seven intact bitches were used as controls. Blood samples for determination of prolactin and progesterone concentrations were collected on days -1, 1, 2, 3 and 7 in the ovariectomized group, and on day 1 and day 7 in the control group. On day 7, the presence or absence of overt pseudopregnancy was recorded. The four ovariectomized bitches with a history of pseudopregnancy showed signs of overt pseudopregnancy (P < 0.01). On day 7, progesterone concentrations were significantly higher in the control than in the ovariectomized bitches (P < 0.01). The expected decrease in serum progesterone concentration after ovariectomy was similar in pseudopregnant bitches and non-pseudopregnant bitches. However, in pseudopregnant bitches, but not in non-pseudopregnant bitches, there was a marked increase (expressed as percentage change) in the concentration of prolactin between day -1 and day 7 (P < 0.01). It was concluded that the abrupt decrease in progesterone concentrations does not lead systematically to pseudopregnancy. Only in bitches predisposed to pseudopregnancy would an abrupt decrease in progesterone concentrations induce a substantial increase in prolactin concentrations, which in turn would trigger the typical signs of pseudopregnancy.

Animals↗