Changes of neuroleukin mRNA levels in hypothalamus pituitary and splenic lymphocytes of rats during cold acclimation

Neuroleukin(NLK),a protein(Mr 56000),acts on both the nervous and the im-mune systems and its expression is regulated at mRNA levels.One hundred fifty Sprague-Daw-ley(SD)male rats were divided into 5 groups:control group(N)and groups of cold-exposurefor 1,2,3 and 4 weeks(ClW,C2W,C3W and C4W).With RNA dot blot experiments,changes of NLK mRNA levels in both neuroendocrine system(pituitary and hypothalamus)andimmune system(splenic lymphocytes,LC)of SD male rats during cold acclimation presentedsimilar responses.C/N ratios of scan gray intensity level in RNA dots are presented as follows:there was a rise in C/N ratio to 1.63～11.31 in CIW,a fall to 0.63 in C2W and a rise again to1.42～21.09 in C3W.It might thus be regarded as a general response to cold surroundings.Itwas reported that SDS-PAGE autoradiogram of synthetic proteins in LC and secretive proteinsin supernatant cultured in vitro showed that NLK content in LC was not parallel to its mRNAlevel because NLK was extremely meager over the 1-week cold exposure whereas it increasedobviously over the 3-and 4-week cold exposure.This is probably a major cause of why im-munoglobulin synthesis in cold-acclimated animals was greatly enlarged.