Formation of GABA via oxidative deamination of putrescine in ovaries of immature rats after gonadotrophin stimulation

Urine GABA levels in ovarian cancer patients: elevated GABA in malignancy

The association of malignancy with elevated diamine oxidase (DAO), an enzyme producing gamma-aminobutyric acid (GABA) is well documented. In ovarian cancer, increased DAO occurs in the malignant tissues and plasma. Since higher DAO levels cause GABA accumulation, elevated GABA may occur in ovarian cancer and be reflected in urine. We tested this hypothesis and found that half the ovarian cancer patients had a clearly elevated urine GABA, a result that is in agreement with previous reports on DAO and malignancy. The published findings on DAO, GABA and malignancy suggest that elevated GABA is associated with cancer. This proposal could lead to a GABA urine monitor or new directions in cancer treatment or research.

Influence of photoinhibition on GABA and glutamic acid levels, and on glutamate decarboxylase activity in the testis and epididymis of the golden hamster

Gamma-aminobutyric acid (GABA) is found in the gonads and accessory reproductive organs, and a direct effect on steroidogenesis and sperm viability and motility has been described. The golden (Syrian) hamster is a seasonal breeder, and a pattern of regression-recrudescence in their reproductive organs is observed when adult animals are exposed to less than 12.5 h daylight for an extended period of time. The purpose of this study was to investigate: (1) the presence of GABA in the testis and epididymis of golden hamsters undergoing regression and spontaneous recrudescence; (2) glutamic acid levels and glutamate decarboxylase (GAD) activity in both tissues, and (3) testicular and epididymal testosterone, dihydrotestosterone and 5 alpha-androstane-3 alpha, 17 beta-diol concentrations. Adult golden hamsters were exposed to long (LP 14L:10D) or short (SP 6L:18D) photoperiods for 9, 12, 14, 16, 18 or 22 weeks. When animals were exposed to SP for 14-16 weeks, the testis and epididymis reached maximal involution. Testicular and epididymal androgen levels showed a marked decrease (p < 0.05) during the regression period, and after 18-22 weeks, values began to recover. Between 12 and 18 weeks in SP, the testicular and epididymal content of GABA and glutamic acid was reduced significantly. The concentration of GABA in both tissues showed a sharp rise (p < 0.05), while the concentration of glutamic acid diminished during the period of maximal involution (p < 0.05). In the testis, GAD activity was increased (p < 0.001) after 14 weeks in SP, with no change in the epididymis. In conclusion, glutamic acid via GAD activity could be the main source of GABA in the testis, but not in the epididymis. Furthermore, the presence of GABA in testicular cells and its subsequent photoperiodic variations might act as an important autocrine and/or paracrine modulatory signal in gonadal processes.

Gamma-aminobutyric acid (GABA) formation from putrescine in guinea-pig liver during ontogenesis

1. The changes in hepatic diamine oxidase (DAO) activity of the foetal and maternal origin and their relations to GABA formation during pregnancy in guinea-pigs are described. 2. Foetal DAO activity continuously increased while the maternal enzyme from the 45th day of gestation onwards decreased. 3. Conversion of putrescine to GABA via oxidative deamination has been detected in the earliest studied day i.e. the 34th.

Metabolism of putrescine in the pregnant rat

The in vivo metabolism of 14C-putrescine injected to rats before, during and after pregnancy was studied. Within 30 min of the administration of the isotope 9-12% of the injected radioactivity was recorded as 14CO2 in the expired air and after 5 h 60% was expired. The radioactivity excreted in the urine during the first day following the 14C-putrescine administration consisted of unmetabolized putrescine, gamma-aminobutyric acid (GABA) and some unidentified compound(s). No radioactive polyamines were detected in the urine. After treatment of pregnant rats with the diamine oxidase inhibitor aminoguanidine the expiration of 14CO2 was almost completely inhibited. In the urine increased amounts of unmetabolized putrescine were excreted while the excretion of GABA and the unidentified compound(s) were decreased. In addition 14C-spermidine appeared in the urine. The in vitro metabolism of putrescine was determined by the incubation of different tissues of pregnant and non-pregnant rats with 14C-putrescine. The 14C-metabolites derived via the diamine oxidase pathway (delta 1-pyrroline, GABA, some unidentified compound(s) and carbon dioxide) varied in magnitude with the tissue investigated. GABA was found to be a main metabolite of putrescine in several tissues of the pregnant rat. The content of putrescine and spermidine was elevated in several tissues as well as the blood on the 19th day of pregnancy in rats treated with aminoguanidine, while the content of spermine was unchanged.