Titres of oestrogen are known to rise from dioestrous to proestrous stage of the oestrous cycle. Such a rising level of estrogen may be responsible for rise in intracellular concentration of cAMP. The estrogen primed tissue, changing from proestrous to oestrous, under known increasing progesterone level and preovulatory LH surge, may led to a sort of balancing action on the varying levels of glycogen synthetase and phosphorylase enzyme activities so as to play a role in maintaining a steady state of glycogen concentration in the salivary gland. Therefore, alterations in glycogen concentration and the activities of concerned enzymes viz. glycogen synthetase, phosphorylase and cAMP-specific phosphodiesterase (cAMP-PDE) have been studied in albino rats. An abrupt but significant drop in cAMP-specific phosphodiesterase (cAMP-PDE) activity was found to facilitate corresponding reduction in glycogen and lowering protein concentration of the gland, during transition from oestrous to metoestrous. Main features of the meteostrous stage were depletion of glycogen and protein concentration. Taking into consideration the alteration of glandular glycogen and protein concentration, during various stages of oestrous cycle, variation in the viscosity of saliva has been suggested; in phase with the cyclicity
