Size heterogeneity of prolactin secreted from and stored in the rat anterior pituitary gland in vitro

The Choroid Plexus Is an Alternative Source of Prolactin to the Rat Brain

Among the more than 300 functions attributed to prolactin (PRL), this hormone has been associated with the induction of neurogenesis and differentiation of olfactory neurons especially during pregnancy, which are essential for maternal behavior. Despite the original hypothesis that PRL enters the central nervous system through a process mediated by PRL receptors (PRLR) at the choroid plexus (CP), recent data suggested that PRL transport into the brain is independent of its receptors. Based on transcriptomic data suggesting that PRL could be expressed in the CP, this work aimed to confirm PRL synthesis and secretion by CP epithelial cells (CPEC). The secretion of PRL and the distribution of PRLR in CPEC were further characterized using an in vitro model of the rat blood-cerebrospinal fluid barrier. RT-PCR analysis of PRL transcripts showed its presence in pregnant rat CP, in CPEC, and in the rat immortalized CP cell line, Z310. These observations were reinforced by immunocytochemistry staining of PRL in CPEC and Z310 cell cytoplasm. A 63-kDa immunoreactive PRL protein was detected by Western blot in CP protein extracts as well as in culture medium incubated with rat pituitary and samples of rat cerebrospinal fluid and serum. Positive immunocytochemistry staining of PRLR was present throughout the CPEC cytoplasm and in the apical and basal membrane of these cells. Altogether, our evidences suggest that CP is an alternative source of PRL to the brain, which might impact neurogenesis of olfactory neurons at the subventricular zone, given its proximity to the CP.

Effect of environment on the intake of food and water, body weight, egg production and plasma concentrations of corticosterone and prolactin in turkey hens

During the first 4 weeks of egg production, there were no differences in the plasma concentrations of prolactin and corticosterone, egg production, body weight and the consumption of food and water between turkey hens which were maintained in cages or in floor pens. The plasma concentration of prolactin increased to the same extent in both environments during the period of peak egg production. A further rise in concentration of prolactin occurred in association with the termination of oviposition in 15 of the 19 hens which stopped laying eggs. Prolactin appeared to be progonadal and then antigonadal, once a threshold concentration was exceeded. This threshold value was higher in caged turkey hens. After laying ended, high concentrations of prolactin in hens maintained in cages were not maintained in the absence of a stimulus or stimuli associated with the nests.

In vitro effects of somatostatin and urotensin II on prolactin and growth hormone secretion in tilapia, Oreochromis mossambicus

The control of release of two recently characterized forms of prolactin (PRL) of molecular mass 24 and 20 kDa was investigated. The rostral pars distalis of male tilapia was incubated singly in a hypotonic modified Krebs-Ringer bicarbonate medium in order to stimulate PRL release; for comparison, the proximal pars distalis containing growth hormone (GH) cells was incubated in isotonic medium with or without 1 microgram/ml cortisol to stimulate GH release. The release of both PRLs and GH into the medium was measured by sodium dodecyl sulfate (SDS)--polyacrylamide gel electrophoresis followed by densitometry. Both somatostatin and synthetic (Gillichthys) urotensin II, a partial somatostatin homolog and analog from the teleost caudal neurosecretory system, significantly inhibited the release of both PRLs. Somatostatin significantly inhibited GH release, but urotensin II had no significant effect.