Third genetic polymorphism of tear proteins Rtp-3 in the rat

Two genetic markers, tear proteins RTP-1 and RTP-2, were studied in six inbred rat strains by the agarose gel electrophoretic method. An RTP-2A fast migrating band was found in M520/W, AUG/W, and BN/Han W strains whereas in WAG/W, L-E/W and SPRD/W rats no RTP-2 band was detectable (Rtp-2b). In the case of RTP-1 there always occurred only one band but with a different migration speed in gel according to the representing allele. The slow band RTP-1B was observed in rat strains WAG/W, AUG/W, SPRD/W, L-E/W, and M520/W, the fast band RTP-1A being observed only in BN/HanW rats. Moreover, a considerable sex difference in the expression of tear protein in all the tested strains was observed. The expression of a third independent rat tear protein locus whose product, controlled by androgens, was found to be present only in females and castrated males. It is proposed to designate it Rtp-3 with three alleles: Rtp-3a, Rtp-3b, and Rtp-3c. The discrepancy of these results with the observation by Kondo et al. concerning Rtp-1 alleles has been discussed.