Patterns of Cyclic AMP Phosphodiesterases in the Rat Pineal Gland:Sex Differences in Diurnal Rhythmicity

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Abstract
Rat pineal cAMP phosphodiesterases (PDE) were studied during male development and in adult females by means of gel electrophoresis, kinetic analysis and diurnal activity measurements. In both male and female rats, 2 molecular forms of PDE coexisted. In neonatal-infantile males (birth to day 20 of age) a 3rd isozyme was detected. The kinetic properties of PDE were essentially similar in infantile and adult male rats with respect to the Km, however, a minimal Vmax was observed at 1000 in adults, but not in neonatal animals, PDE activity in male rats was maximal between 0200 h and 0400 h, and also at 0400 h, and was minimal at 1000 h. This pattern appeared to develop during the infantile period of life. The pattern of activity observed in adult female rats was similar to that of adult males, except that it lacked a pronounced afternoon peak. The diurnal PDE activity profile of castrated male adult rats was similar to female animals and testosterone substitution in male castrated rats resulted in a pattern which resembled that of adult male controls. In addition to the above measurements, testosterone serum levels were determined during all of these experiments.