Endogenous regulation of the pineal melatonin secretion in Gallus domesticus

The serum melatonin (MT) levels in laying hens (Gallus domesticus) subjected to different light/dark (L/D) cycles have been measured. In order to study the levels of circulating MT in blood it was necessary to establish a specific and very sensitive radioimmunoassay (RIA). Our MT-RIA was developed after raising anti-MT antibodies in Rabbits. The RIA was performed by using3H-MT as tracer. The standard curve covered the range of 0.022–0.345 pmol/vial and theK D value for MT was estimated at 1.37×1010 l/mol. The antiserum specificity has been analysed; none of the common MT analogues showed cross-reactivity strong enough to interfere with MT measurement. The intra- and inter-assay variability for serum samples were 7.2 and 15.3%, respectively.