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VALDEZ Susana Ruth

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Título:

EFFECT OF MILD HYPERTHYROIDISM ON GLUCOCORTICOID SECRETION INDUCED BY ACUTE STRESS IN PREGNANCY AND LACTATING RATS

Autor/es:

NEIRA FLAVIA J; PIETROBON ELISA O; SANCHEZ MARÍA BELÉN; MORENO SOSA MARÍA TAMARA; SOAJE, MARTA; JAHN GRACIELA A; VALDEZ SUSANA RUTH

Lugar:

Mendoza

Reunión:

Congreso; XXXVI Reunión Anual de la Sociedad de Biología de Cuyo; 2019

Institución organizadora:

Sociedad de Biología de Cuyo

Resumen:

Disorders in thyroid functionare associated with anxiety and depression. Therefore, responses to stress maybe altered in patients with thyroid diseases. Stress is associated withfunctional changes in brain areas such as the hippocampus (HpC) and medialbasal hypothalamus (MBH) by activating the hypothalamic-hypophysis-adrenal axis(H-H-A) and the consequent release of glucocorticoids in response to thestressor. In this study we analyzed the effects of mild hyperthyroidism oncorticosterone response (measured by RIA) to acute stress (exposure to ethervapors for 2 min.) and on the expression (by qPCR) of the glucocorticoidreceptor (GR) and the long isoform of the prolactin receptor (PRLRL) in MBH and HpCin Wistar female rats in different reproductive states (day 19 of gestation(G19), 2 (L2) and 12 (L12) of lactation). Hyperthyroidism (hyperT) was inducedwith T4 (0.1mg /kg/day, s.c.) a dose of that allows the maintenance oflactation. Control (Co) and hyperT rats were bled from the tail vein during the2 min ether exposure (s1) and 5 min after ether exposure (s2). In G19 acutestress induced corticosterone release in Co group (P<0.001), while in hyperT group no response was observed,but basal levels of the hormone were elevated (P<0.05 vs. Co). In L2 corticosterone release wasincreased by stress in both Co and hyperT groups (P<0.001and P<0.05 respectively) and the hyperTgroup showed increased basal levels (P<0.01). In L12 ether stress increased corticosterone releasein the hyperT group (P<0.001), while the Co group showed unchanged levels. In MBH the expression of GRin the Co group increased in L2 compared with G19 (P<0.05)and remained at the same levels in L12. Inthe hyperT group an increase of GR expression in L12 was observed with respectto G19 and L2 (P<0.01). The expression of PRLRL in the Co group increased in L12 compared with G19 andL2 (P<0.01), while hyperTadvanced the increase of PRLRL expression to L2 compared with G19 (P<0.05). On the other hand, hyperT increased PRLRL expression on L2compared with the Co group (P<0.05). In HpC the expression of the GR increased in L12 withrespect to G19 in both groups (Co P<0.05 andhyperT P<0.001). No effects of hyperTnor of reproductive stage were observed in HpC PRLRL expression. Oncelactation is established, the H-H-A axis is still reactive in hyperT rats inresponse to an acute stress evidenced by adrenal corticosterone release,whereas in Co rats the axis show a physiological adaptative hyporeactivity. Theseevidences indicate that mild hyperthyroidism induces a differential expressionof hippocampal and hypothalamic GR and PRLRLat early lactation that could be involvedin the maintenance of the H-H-A axis reactivity.

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