Respuesta diferencial al estrés y a esteroides ováricos entre la cepa de ratas hipoprolactinémicas OFA hr/hr y Sprague Dawley.

VALDEZ, SUSANA R; DEIS, RP; JAHN GA

Mar del Plata

Congreso; XLVIII (SAIC) y (SAI).; 2003

SAIC/SAI

DIFFERENTIAL RESPONSE TO STRESS AND OVARIAN STEROIDS BETWEEN THE HYPOPROLACTINEMIC STRAIN OFA hr/hr AND SPRAGUE DAWLEY RATS. S.R. Valdez, R.P. Deis, G.A. Jahn LARLAC-IMBECU, CC 855, 5500 Mendoza, Argentina. Email: gjahn@lab.cricyt.edu.ar The Sprague Dawley (SD)-derived OFA hr/hr rat strain, shows deficient lactation, hypoprolactinemia, altered dopaminergic regulation of PRL and enhanced response to stress compared with Wistar rats. We studied the effect of two moderate stressors (moving to an other room and anesthetized with ether) on OFA and SD rats under different hormonal environments. Cyclic rats (Pro-oestrus, Estrus, Diestrus 1 and 2), rats on day 19 of pregnancy (P19) and on day 11 of lactation (L11), or ovariectomized (OVX), OVX plus estrogen (OVX+Eg 5 ug), OVX plus progesterone (OVX+Pg 5 mg x 2), OVXEgPg, and males with and without Eg were used.Groups of 8 rats were moved to a contiguous room within the animal house and subsequently exposed to ether for 2 min. Rats were bled from the tail vein (S1) during the 2 min ether exposure and 5 min after ether stress (S2). Basal samples were taken under light ether anesthesia in the animal house.Serum PRL, measured by RIA, was higher on estrus, and the response to stress was higher in SD (Co 37±7, S1 297±42, S2 210±32 ng/ml) than in the OFA strain (Co 34±8, S1 68±13, S2 176±38). There were no differences on the other days of the cycle and in males. PRL levels were increased only in OFA rats in P19 and L11 (P19 Co 5.5±1.9, S2 13.6±2.8 and L11 Co 2.6±0.5, S2 24± 4). In OVX rats the response was higher in SD than in OFA rats. SD rats with OVX+Eg had high basal PRL and the response was higher compared with OFA rats (SD Co 108±26, S1 280±68, S2 143±32; OFA Co 17±4, S1 45 ±13, S2 87±16). OVX+Pg blocked the response to stress in both strains. In the OVX+EgPg groups, basal levels were low in both strains and the response to stress was inhibited in SD but not in OFA rats. OFA rats showed similar or smaller response to stress than SD and lower response to estrogen. Nevertheless, the results obtained in pregnant, lactating or Pg-treated rats indicate a lower capacity of Pg to inhibit the stress response in OFA rats.