[The activity of melanin-aggregating hormones in the blood and eyes in the early postnatal development of rats].

: The activity of melanin-aggregating hormones (MAH) in the blood serum and homogenates of the eyes in four strains of rats was determined using the method of bioassay on dermal melanophores of tadpoles (Rana temporaria). This test-system is sensitive to melatonin at concentration of 25.1 mg/ml and higher. MAH is detected in the blood at 9th and in eye homogenates at 15th days after birth in grey Norway rats, while in albino Wistar and pale hooded Campbell rats with hereditary retinal degeneration MAH is observed at the 3rd and 4th postnatal days respectively. No increase of MAH activity is found in black hooded Hunter rats with inherent retinal degeneration during the first five days after birth. Thus, Wistar and Campbell rats differ significantly from grey and Hunter rats by MAH activity in the blood and eyes during early postnatal development.