Some factors affecting [3H]tyrosine binding to plasma membrane preparation of rat corpora lutea in vitro

Temperature, pH, enzymes and ions affected the two types of [3H]tyrosine binding sites differently. The optimal temperature and pH for the high affinity sites were 24 C and 7.4, and for the low affinity sites 37 degrees C and 7.0, respectively. The [3H]tyrosine binding to the high and low affinity sites was not observed at 55 degrees C, nor at pH 6.0 or pH 8.5. Trypsin reduced [3H]tyrosine binding to the high affinity sites, but had no effect on the binding to the low affinity sites. Neuraminidase reduced [3H]tyrosine binding to the low affinity sites, but had no effect on the binding to the high affinity sites. None of cycloheximide, kCG, cAMP, and progesterone affected [3H]tyrosine binding.