Variations in the cellular proliferation of prolactin cells from late pregnancy to lactation in rats.
Lactation is a physiological process associated with hyperactivity of hypophyseal prolactin-producing cells. It is known that the percentage of these cells is increased during lactation, although there are discrepancies in the reports regarding the mechanisms responsible for increasing the number of prolactin cells. In order to analyse whether this increase is a result of previous proliferation, variations in the proliferation rate of prolactin-positive cells were determined from late pregnancy to lactation in adult female rats by means of observation of the immunohistochemical expression of PCNA as a marker of cellular proliferation. During late pregnancy, a very significant increase in the percentage of proliferating prolactin cells was observed in comparison to non-pregnant females in the proestrus phase (p < 0.01). Although the percentage of prolactin-positive cells after one week of lactation was higher than in non-lactating or in pregnant females (p < 0.01), the proliferation rate was lower than in the other groups studied. In sum, our results suggest that late pregnancy constitutes a preliminary proliferative phase preparatory to the ensuing lactation phase and that endocrine changes in late pregnancy involve the cellular proliferation of hypophyseal prolactin cells in order to prepare the gland for later demands and to prevent proliferative changes from occurring during lactation.
Laboratorio de Neuroendocrinología, Instituto de Neurociencias de Castilla y León, Departamento de Anatomía e Histología Humanas, Facultad de Medicina, Universidad de Salamanca, Avda. Alfonso X El Sabio s/n, 37007 Salamanca, Spain. jcar@usal.es
José
J
Carretero
Manuel
M
Rubio
Enrique
E
Blanco
Deborah J
DJ
Burks
José L
JL
Torres
Elena
E
Hernández
Pilar
P
Bodego
José M
JM
Riesco
Juan A
JA
Juanes
Ricardo
R
Vázquez
D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002455:Cell Division / Q000502:physiology; D005260:Female; D007150:Immunohistochemistry; D007774:Lactation / Q000502:physiology*; D010903:Pituitary Gland, Anterior / Q000166:cytology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D011359:Proestrus / Q000502:physiology; D011388:Prolactin / Q000378:metabolism*; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley
D015415:Biomarkers; D018809:Proliferating Cell Nuclear Antigen; D011388:Prolactin