REGULATION OF THYROID HORMONE RECEPTORS BY SUCKLING IN RATS WITH NORMAL OR DEFICIENT LACTATION.

PENNACCHIO GE; NEIRA FJ ; VALDEZ SR; JAHN GA; SOAJE M

Buenos Aires

Congreso; 62 Reunión Científica Anual de la Sociedad Argentina de Investigación Clínica.; 2017

SAIC

During lactation, sustained hyperprolactinemia is maintained bythe suckling stimulus and decreased hypothalamic sensitivity toprolactin (PRL) negative feedback, that maintains a reduced dopaminergictone. OFA (hr/hr) rats, derived from the Sprague Dawley(SD) strain have deficient lactation, high hypothalamic dopaminergictone and a blockade in suckling induced PRL release. Hyperthyroidrats also have deficient lactation, caused by increased hypothalamicsensitivity to PRL negative feedback that leads to a partial blockadein suckling induced PRL release. Thus, both groups show elevateddopaminergic tone responsible for the decreased PRL release andlactation failure. This evidence suggests that thyroid hormones maybe also involved in prolactin regulation during lactation. We investigatedthe changes in hypothalamic thyroid hormone receptors (TR)expression in response to the suckling stimulus in OFA rats comparedto SD rats (normal lactation). Using real time quantitative RTPCR,we measured the changes in hypothalamic mRNA expressionof TRβ isoforms 1 and 2 and TRα isoforms 1 and 2, in mid-lactatingOFA and SD rats, continuously suckled (CL), separated from theirpups for 12 h (Sep), or separated and subsequently suckled during2 (S2) or 4 (S4) h. We also determined serum PRL levels by RIA andlitter weight gain. After suckling, PRL release and litter weight gainwere higher (p