Expression of Cysteine Sulfinate Decarboxylase mRNA in Rat Mammary Gland.

Abstract

ABSTRACT. Our previous report demonstrated that high concentration of taurine is present in rat milk for the first few days of lactation and plays an important role in the body growth of rat pups. In the present study, gene expression of rate-limiting enzyme for taurine biosynthesis, cysteine sulfinate decarboxylase (CSD) were examined in rat mammary gland. By RT-PCR, CSD mRNA was found to be expressed in rat mammary gland like that in the liver. The expression level of CSD mRNA in the mammary gland was higher in the earlier lactational stage (days 1 and 6 of lactation) than that in the later lactational stage (day 14). CSD mRNA expression in the mammary gland of non-pregnant rats was only a trace level. By in situ hybridization analysis, CSD mRNA was demonstrated in the epithelial cells of the mammary gland. These results suggest that high concentrations of taurine in the milk are at least partially resulted from de novo synthesis of taurine in mammary gland epithelial cells and that the expression pattern of CSD mRNA may be responsible for the changes in taurine levels in the milk during a lactational period.KEY WORDS: CSD mRNA, liver, mammary gland, rat, taurine.J. Vet. Med. Sci. 62(8): 829-834, 2000 It is well known that in many mammalian species a high concentration of taurine occurs in milk and that taurine is necessary for offspring during developmental stages [3,11]. We have also recently shown that high concentrations of taurine, especially at the beginning of lactation, is mandatory for normal body growth of rat pups presumably by maintaining insulin-like growth factor-I (IGF-I) levels in the blood [5]. Taurine in milk is thought to be derived from the liver, because the milk taurine level was positively correlated with hepatic taurine concentration during a lactational period [15]. The hepatic taurine pool appears to increase just before parturition and rapidly decrease after the first few days of lactation when high levels of taurine are secreted into the milk [15]. However, the data in our previous study indicated that taurine concentrations in milk always highly exceeded those in dams' peripheral circulation, and administration of β-alanine, a transport antagonist of taurine, to lactating dams did not decrease taurine concentrations in the milk [5]. These observations make us hypothesize that taurine can be synthesized by the mammary gland, and that taurine synthesized in the mammary gland may be another important source of taurine in the milk.While several possible pathways have been proposed for taurine synthesis, the most widely accepted pathway involves the oxidation of cysteine to cysteine sulphinic acid (CSA). CSA may be either decarboxylated, transaminated or oxidized. Decarboxylation of CSA by cysteine sulfinate decarboxylase (CSD) leads to hypotaurine, which can be further oxidized to taurine. Oxidation of CSA produces cysteic acid, which then may be decarboxylated by CSD to taurine. Thus, CSD is considered to be the main rate-limiting enzyme for taurine synthesis. The enzymatic activit...

Changes in messenger RNA abundance of amino acid transporters in rat mammary gland during pregnancy, lactation, and weaning

“…These results are in agreement with those observed in microarray analysis that showed a reduction in the expression of this transporter in mice mammary gland during lactation in comparison with pregnancy [43]. The expression of the rate-limiting enzyme required for taurine synthesis, cysteine sulfinate decarboxylase (EC 4.1.1.29), is highly induced during pregnancy and lactation [51,52], suggesting that taurine might be synthesized de novo in the mammary gland and not only transported from the blood.…”

Taurine, energy drinks, and neuroendocrine effects

“…45 The rate-limiting enzyme of the predominant pathway is thought to be cysteine sulfi nate decarboxylase (CSD), and its presence within an organ indicates involvement in taurine production. 44 CSD has been found in the liver, 46 the primary site of taurine biosynthesis, as well as in the retina, 47 brain, 48 kidney, 49 mammary glands, 50,51 and reproductive organs. 52…”

Effects of taurine on male reproduction in rats of different ages

“…As a semi-essential amino acid, taurine is rich in many tissues, and can be biosynthesized by many tissues, such as the central nervous system [2], liver [3], kidney [4], retina [5] and mammary gland [6]. In the male reproductive system, taurine has been detected in Leydig cells, vascular endothelial cells, and some other interstitial cells of testis and epithelial cells of efferent ducts in rats [7].…”