Because of limited sources of rRTF, oRTF preparations were used to determine which factors in RTF were responsible for regulating GGT catalytic activity and protein level. Results showed that both charcoal-extracted oRTF and no-ABP oRTF recovered GGT catalytic activity and protein level in the initial segment following EDL (Figs. 3 and 4). As almost no ABP is present in no-ABP oRTF, and limited amounts of testosterone were present in charcoal-extracted oRTF and no-ABP oRTF, the recovery of GGT catalytic activity and GGT protein level in the 3-day-EDL initial segment by charcoal-extracted oRTF and no-ABP oRTF (Figs. 3 and 4) is probably not due to ABP or testosterone in these preparations. Buy Asthma Inhalers Online

It is suggested that the active regulators in oRTF are protein-like because inactivation of proteins by boiling the oRTF did not bring about recovery of GGT activity (Fig. 3). The molecular mass of such proteins in oRTF was shown to be greater than 10 kDa, as indicated in Figure 4. When the findings are taken together, factors other than ABP or testosterone in oRTF preparations, which can regulate the GGT catalytic activity and GGT protein level in the initial segment of the rat epididymis, appear to be proteins of molecular mass greater than 10 kDa. These results support previous observations that proteins of greater than 10 kDa in oRTF or ram RTF are beneficial for the maintenance of cultured principal cells from the proximal epididymal regions to metabolize testosterone and to stimulate protein secretion in the initial segment.