Role of Ammonia and Nitric Oxide on The decrease of Plasma Prolactin Levels in Prehepatic Portal Hypertensive Male Rats.

DE LAURENTIIS, A; SCORTICATI, C; PERAZZO, J C; RETTORI, V

Buenos Aires, Argentina

Congreso; XXII CONGRESO LATINOAMERICANO Y 1RO IBEROAMERICANO DE CIENCIAS FISIOLÓGICAS; 2006

SAFISIOL (Sociedad Argentina de Fisiología)

Rat with prehepatic portal hypertension (PH) is a model of porto systemic hepatic encephalopathy (PSHE). Since very little is known about the neuroendocrine changes that occur in PSHE and considering that prolactin (PRL) plays an important role in the maintenance of the organism homeostasis, in the present study we evaluate plasma PRL levels in an adult Wistar male rat with PH and also study the involvement of hyperammonemia, nitric oxide (NO) and dopamine (DA) in the control of PRL secretion in this model. We determined plasma PRL levels by RIA, DA and dihydroxyphenylacetic acid (DOPAC) content in medial basal hypothalamus (MBH) and anterior pituitary (AP) by HPLC. In addition, NO synthase (NOS) activity and protein expression were evaluated in AP by 14C-Arginine method and Western blot respectively. Also, the AP from normal and PH rats were incubated under different concentrations of ammonia and/or a NOS inhibitor (L-NAME) and PRL secretion was determined. Our results showed that plasma PRL level was significantly decreased in PH rats. However, we did not observe modifications in DA nor DOPAC content, neither DOPAC/DA ratio in both MBH and AP. Moreover, NOS activity and protein expression were increase in AP from PH rats. The ammonia significantly reduced PRL secretion from AP in vitro. The presence of L-NAME abrogated the inhibitory effect of PH plus ammonia on PRL secretion. In conclusion we found that plasma PRL levels were decreased in PH rats, probably due to the high ammonia levels and the increase in NOS activity and/or content in AP. The increase NO production inhibits PRL secretion from AP, regardless of the participation of the dopaminergic system.