Serum oestrogen, progesterone and prolactin concentrations in cyclic, pregnant and lactating beagle dogs

Abstract

Summary. No correlations between the three hormones measured were found in any of the reproductive states examined. In 2 out of 8 dogs a negative correlation between serum progesterone and prolactin levels was found at Day 11 and Day 15, respectively (Day 0 = first day of copulation). In all of the 8 animals in which the progesterone and prolactin concentrations were measured in the same samples in late pregnancy, a negatively correlated overall pattern was obtained between both hormone profiles. No correlation between serum oestrogen and prolactin levels was found.It is concluded that the proliferative mammary gland changes which are induced in female dogs during long-term toxicity testing with progestagens are unlikely to be related to prolactin or oestrogen synthesis and/or secretion.

Oestrogen and progesterone concentrations in peripheral blood in pregnant red foxes (Vulpes vulpes)

“…Moller (1973) describes a resemblance between the profiles of progesterone secretion in pseudopregnant and pregnant blue fox females but does not comment on the persistence of corpora lutea in this species. In the bitch also, similar progesterone secretion profiles in pregnancy and pseudopregnancy have been observed by Smith & McDonald (1974), Hadley (1975) and Graf (1978). Smith Previous work has demonstrated that pituitary secretions are involved in the persistence of the corpora lutea in the red fox (Bonnin-Laffargue et al, 1972).…”

“…Hadley (1975) also failed to observe the fall in progesterone concentrations after oestrus and subsequent large rise to peak gestational levels 19-24 days after the first day of oestrus which was described by Smith & McDonald (1974). Graf (1978) has confirmed the observations of Smith & McDonald (1974) and suggested an extra-ovarian source of progesterone for the second increase in serum progesterone concentration observed, which coincides with the time of implantatio'n. We have been unable to clarify the question of whether the corpus luteum is the major site of progesterone production in the red fox.…”

“…in the ewe (Bassett, Oxborrow, Smith & Thorburn, 1969), coypu (Rowlands & Heap, 1966) and rat (Wiest, 1970). A similar profile of progesterone secretion during pregnancy is observed in other canids, such as the blue fox (Moller, 1973) and the domestic dog (Parkes, Bell & Christie, 1972;Smith & McDonald, 1974;Hadley, 1975;Graf, 1978). These observations seem to indicate that, in canids, luteotrophic factors originating from the placenta do not influence the corpus luteum function.…”

“…Laparotomy and ovari¬ ectomy in early pregnancy cause abortion (unpublished). Despite individual differences, pregnant foxes showed only a non-significant decline in peripheral progesterone before parturition, unlike the blue fox (Moller, 1973) and the bitch (Smith & McDonald, 1974;Graf, 1978) Text- fig. 1.…”

“…The absence of a decline in peripheral plasma progesterone levels and of a pre-partum rise in oestrogens in the fox raises the question of the mechanism of the initiation of'parturition. Graf (1978) has suggested that prolactin is involved in the termination of pregnancy in the bitch and this hormone should, therefore, also be studied in vixens.…”