RELATIONSHIP BETWEEN PLASMA TESTOSTERONE AND URINARY FELININE IN THE GROWING KITTEN

Felinine, a unique amino acid the functions of which are not well unde rstood, is found in large quantities in male cat urine. Our study ran for 13 calendar months and involved taking monthly samples of blood an d urine from 10 male and 10 female kittens starting at 6 months of age and measuring urinary felinine and plasma testosterone concentrations . Felinine was detectable at 6 months of age in all cats (range, mean +/- SEM, nmol/mL, 13.8-801.1, 432.3 +/- 112.2, males and 34.3-393.0, 1 40.4 +/- 45.0 females). In entire males, felinine showed a biphasic pa ttern, peaking (2550 nmol/mL) between 11-13 months of age toward the e nd of the attainment of puberty then falling to a low (1048 nmol/mL) a t 15 months of age then climbing to a peak (3661-nmol/mL) at 17 months of age. Natural plasma testosterone levels in entire males showed a s imilar biphasic pattern peaking (6.8 pmol/mL) at 12 months of age, fal ling (1.3 pmol/mL) at 15 months, and finally rising again (12.6 pmol/m L) at 16 months of age. Castration of half the male cats induced a par allel fall in both testosterone and felinine that was reversed followi ng testosterone supplementation. Urinary felinine levels in entire fem ales rose slowly throughout the study and reached 795 nmol/mL at 18 mo nths of age compared to the level of 365 nmol/mL reached by the spayed females: these levels were not significantly different when expressed as felinine/creatinine ratios. We could not detect testosterone in ei ther entire or spayed females and so concluded that felinine was unrel ated to testosterone in these groups. There was strong evidence that p lasma testosterone levels are positively correlated with urinary felin ine levels in male cats. The control of felinine might be sex-linked a nd may be part of a pheromonal signaling process of the male cat. (C) 1998 Elsevier Science Inc.