Paper Title
Pharmacological Aspects and Potential New Clinical Applications of Taurine and Bromocriptine

Our previous work has shown that high plasma taurine levels was found in hyperprolactinaemic patients; these levels returned to normal after bromocriptine (dopaminergic agonist, D2) treatment for three months. Furthermore we reported that bromocriptine decreased the myometrial PGI2 release in rats; whereas taurine increased the content of the myometrial PGI. It was suggested that the activity of Na (+)-K (+)-ATPase could modulate the production of PGs in several tissues. Bromocriptine is shown to stimulate Na + /K + -ATPase in the liver of rats, while taurine inhibits sperm plasma membrane Na + /K+-ATPase. It is therefore, thought of interest to investigate the effect of bromocriptine, taurine or their combination on the isolated rabbit jejunum and on the rat uterus in vitor and in vivo. Methods, the effect of bromocriptine on isolated tissues and after pretreatment of the tissue with sulpiride, haloperidol, cyproheptadine or taurine were studied in vitro. Rabbit jejunum and rat uterus (in estrus) were obtained and suspended at 37°C in oxygenated Tyrode's and DeJahlon's solutions respectively. Isotonic contractions were measured using Bioscience Isotonic Transducers In vivo treatment was also carried out to study the effects of bromocriptine mesylate 10mg/kg, taurine 200 mg/kg; or bromocriptine mesylate 10mg/kg + taurine 200 mg/kg, compared to a control group, in order to measure uterine Na+, K+-ATPase activity . The drugs were injected intraperitoneally daily for 14 days. Bromocriptine 0.1 - 0.26 mM stimulated the isolated rabbit jejunum and the rat uterus. Sulpiride and haloperidol failed to antagonize the induced contractions. The latter were abolished by pretreating the tissues with cyproheptadine or taurine. ATPase from rat’s uterus, pretreated with bromocriptine, showed significantly (P < 0.01) higher activity compared to controls. Taurine, on the other hand, caused a significant inhibition of the uterus Na + / K + -ATPase activity. Pretreatment with both taurine and bromocriptine abolished completely the effects of either bromocriptine or taurine alone on the uterus Na +/ K + -ATPase activity. In conclusion, these results showed that bromocriptine and taurine were acting by clearly antagonistic mechanisms in the uterus in vivo and in vitro. The ability of taurine to inhibit uterine Na+, K+-ATPase activity, together with its role as an endogenous regulator of PGs, point to the functional correlations between taurine, PGs and K+-ATPase activity in the uterus. Thus, the result of the present study gives strong evidence for physiological and pharmacological roles of taurine in different clinical fields. Keywords - Bromocriptine, Taurine, Rabbit’s Jejunum, Rat’s Uterus,