Saliva cortisol and testosterone in the guinea pig: Measures for the endocrine function of adrenals and testes?

Abstract

For collection of saliva, cotton buds (Q-tips) were inserted into the guinea pig's cheek pouch, parallel with the cheek teeth. Within 5 min, sufficient fluid was collected for cortisol and testosterone measurements. In saline-treated animals, saliva cortisol and testosterone were about 15 ng/mL and 1.5 ng/mL, corresponding to plasma levels of 52 ng/mL and 5.9 ng/mL. Within 2–4 h after administration of 20 IU ACTH, saliva and plasma cortisol concentrations were strikingly elevated: saliva: 125 ng/mL (2 h), 157 ng/mL (4 h); plasma: 458 ng/mL (2 h), 736 ng/mL (4 h). This treatment did not influence testosterone in saliva, but reduced it in plasma (2.4 ng/mL (4 h)). In animals receiving 100 IU HCG, saliva testosterone remained unchanged, whereas its plasma levels were markedly raised (9.6 ng/mL (2 h), 12.5 ng/mL (4 h)). These results show that saliva cortisol offers promise as a noninvasive method of monitoring changes in guinea pig adrenocortical function. Saliva testosterone, on the other hand, does not correlate with plasma values; hence it cannot be used to assess testicular function in the guinea pig.