Exocrine secretion of immunoreactive erythropoietin from the rat submaxillary gland

The physiological role of immunoreactive erythropoietin (iEp) in rodent submaxillary glands (SMG) is largely unknown. We studied in vivo the effects of cholinergic and adrenergic agents in male rats with respect to exocrine secretion of iEp into saliva. Intravenous administration of metacholine (20 micrograms/kg), norepinephrine (30 micrograms/kg), and isoproterenol (30 micrograms/kg) resulted in equal volumes of saliva over 1 h. None of the drugs altered circulating plasma levels and kidney concentrations of iEp. Salivary secretions induced by either norepinephrine or isoproterenol, both adrenergic agonists, contained high levels of iEp and a significant depletion of gland content was observed, suggesting that SMG exocrine iEp secretion is mediated by adrenergic receptors. In contrast, metacholine-stimulated glands retained their full iEp content and iEp was undetectable in saliva, indicating that cholinergic activity is not associated with exocrine secretion of iEp from SMGs.