Effects of prostaglandins and of leukotriene C4 on the metabolism of labelled glucose in uteri isolated from ovariectomized-diabetic rats. Influences of 17-beta-estradiol and of insulin

An overview of Argentine contributions to diabetes research in the decade of the 1990s

Argentina has a longstanding tradition of diabetes research, beginning with the seminal work of Prof. Bernardo A. Houssay, who was awarded the first Nobel Prize in Medical Sciences for his studies on the relationship between diabetes and pituitary function. Prof. Luis F. Leloir, who was also awarded the Nobel Prize for his work in carbohydrate metabolism, also inspired younger generations of biologists to work in the field of diabetes research. The aim of this paper is to provide a review of the contributions of Argentine researchers during the 1990s. This manuscript includes only reports of Argentine researchers working on diabetes in local laboratories and quoted in Medline. Thus, important contributions not reported in journals included in Medline or produced by Argentine researchers working abroad may have been omitted. The material consists of a brief description of clinical research (epidemiology and costs, metabolic control, associated risk factors, immunological aspects, and other clinical studies) and basic research (animal model with spontaneous diabetes, islet morphology and function in normal and pathological conditions, insulin action, metabolic disorders related to diabetes, and some miscellaneous effects related to drug-induced diabetes). Altogether, a broad idea of the continuous contribution of our national research to the international field of diabetes is provided, as well as a list of Argentine researchers and research centers devoted to the study of diabetes.

Effect of a restricted diet on the metabolism of glucose in uteri isolated from immature rats: influence of indomethacin and nordihydroguaiaretic acid

In immature female rats (21 days), a restricted diet (50% of the daily normal intake for 25 days) interrupts sexual development, leaving animals in a state of sexual immaturity. Food restriction does not affect the use of glycogen in uteri isolated and increases 14CO2 production from U14C-glucose in relation to animals receiving normal feeding that reach sexual maturity. Indomethacin and acetylsalicylic acid stop the increase of glucose metabolism produced by underfeeding, without affecting the uteri of rats receiving normal feeding. The addition of PGE2 and PGF2alpha changes the inhibitory effect of indomethacin. Nordihydroguaiaretic acid produces the opposite effect, increasing glucose metabolism only in uteri isolated from immature animals. These results show that immature animals have a higher glucose metabolism if compared to mature rats. The restricted diet, which slows down sexual maturity, keeps this parameter high due to the influence of some eicosanoids.

Effects of inhibitors of nitric oxide synthase on isolated uteri of fasting rats

The effects of inhibitors of nitric oxide synthase on the glucose metabolism of uteri isolated from 4-day underfed rats were studied. In control rats receiving normal feeding, the addition of indomethacin (5 x 10(-6) M); acetyl salicylic acid (10(-4) M); 400 microM of N(G)methyl-L-arginine, (L-NMMA) or 400 microM of sodium nitroprusside (SNP), does not modify the production of 14CO2 from U14C-glucose. On the contrary, in fasted rat uteri, indomethacin increases glucose oxidation significantly, while acetyl salicylic acid does not alter it. Also, the addition of L-NMMA has no effect. In another group of experiments, in the preparations containing indomethacin of uteri isolated from underfed rats, the addition of L-NMMA significantly changes the effect of indomethacin. Another inhibitor of nitric oxide synthase, N(omega)nitro-L-arginine methyl ester (L-NAME), or hemoglobin (2 microg ml(-1)) a nitric oxide scavenger have the same effects while N(omega)nitro arginine-D-methyl ester (D-NAME) does not. However (SNP), a nitric oxide donor, does not alter the production of 14CO2 in uteri isolated from fasted rats. These results show that in underfed rats, indomethacin increases glucose oxidation independently from its inhibiting effect on cyclooxygenase. Specific inhibitors of nitric oxide synthase can reverse this effect.

Prostaglandin modulation of mouse and human sperm capacitation

To determine whether prostaglandins produce a capacitation and/or acrosome reaction, the effect of prostaglandins on capacitated mouse spermatozoa and the effect of prostaglandin pre-incubation on human and mouse spermatozoa were studied. Prostaglandins did not induce an acrosome reaction in capacitated mouse sperm. PGE1 pre-incubation in a protein-free medium enhanced acrosome loss of mouse sperm challenged with A-23187 or solubilized mouse zona pellucida. Human sperm were pre-incubated in media containing prostaglandins, and an acrosome reaction was induced with calcium ionophore or human follicular fluid. PGE1 pre-incubation enhanced acrosome loss by human sperm when the action was induced with calcium ionophore, but had no effect on follicular fluid induction. We conclude that PGE1 acts as a capacitating factor in vitro for mouse spermatozoa, and enhances acrosome-reaction induction with calcium ionophore in human spermatozoa.

Prostanoid modulation of glucose transport in isolated diabetic rat uterus

3-O-14C-methyl-D-Glucose (3-O-MG) transport and 14C-saccharose incorporation were measured in isolated uterine strips from ovariectomized-estrogenized diabetic rats. Glucose transport was decreased in uterine strips from diabetic rats compared with control animals. PGE1 and PGE2 (10(-7) M) stimulated 3-O-MG transport, PGF2 alpha failed to modify this parameter at the same concentration, while insulin (0.5 U/ml) evoked an improvement 30% greater than PGs. In spite of the negative influence exerted by TXA2 over glucose metabolism in the isolated rat uterus, U46619, 10(-5) M (a TXA2 analogue), and OKY064, 10(-7) M (an inhibitor of TXA2 synthesis), failed to modify basal or insulin-treated hexose transport. Neither additive or synergistic interactions between PGE1 or PGE2 (10(-7) M) and insulin at 0.5 U/ml and 0.25 U/ml were detected. We conclude that the stimulatory action of PGE1 and PGE2 on glucose metabolism that has been previously described by us, involves enhancement of glucose transport.

The role of nitric oxide in the metabolism of labeled glucose in isolated rat uterus. Influence of 17 beta-estradiol

The influence of nitric oxide (NO) on the production of 14CO2 from labeled glucose in uteri isolated from ovariectomized-estrogenized rats was studied. Nitroprusside, an NO donor (NP), 200 microM increased the formation of labeled CO2 from [U-14C]glucose. This effect was blunted by hemoglobin (Hb) 20 micrograms/mL, an NO scavenger. The addition of N-monomethyl arginine (NMMA), an inhibitor of NO synthase decreased the stimulatory action of NP at 400 mM. Incubation of uterine strips in the presence of NP plus acetylsalicylic acid (ASA) 10(-4) M (a cyclooxygenase inhibitor), inhibited the stimulatory action of NP on glucose metabolism. PGE2 (10(-7) M) added to the incubation medium containing NP and ASA reversed the effect of the inhibitor. Neither NP nor Hb nor NMMA modified the 14CO2 production from labeled glucose in uterine strips from ovariectomized rats. The addition of NP to the incubating medium increased PGE accumulation by uterine strips from rats treated with estradiol, but not in ovariectomized animals. These results suggest that NO exerts a positive influence on glucose metabolism and PGE synthesis in isolated rat uteri from estrogenized animals.

Relationship between mouse liver delta 9 desaturase activity and plasma lipids

This study was undertaken to investigate the total plasma fatty acid composition and the relationship between plasma triacylglycerol (TG) levels and liver delta 9 desaturase activity in mice fed n-3 and/or n-6 fatty acid or hydrogenated coconut oil (HCO) (maximum 25 mg/g) supplemented diets. Generally, plasma TG levels and delta 9 desaturase activity were inversely correlated with the ratio of the sum of long chain n-6 fatty acids to 18:2n-6 and to the ratio of the sum of long chain n-3 fatty acids to 18:n-3, but they were positively correlated with the ratio of products and substrates (18:1/18:0) of the enzyme in plasma total lipids. The n-3 fatty acid (mainly 20:5n-3) enriched diet, when compared to the HCO diet at 21 d, caused a significant reduction in plasma TG levels but not in delta 9 desaturase activity. However, a marked reduction in plasma TG content (50-60%) and delta 9 desaturase activity (55-70%) was observed when both 20:5n-3 and 18:3n-6 were supplemented in the diet. The plasma TG levels and delta 9 desaturase activity rose again when the animals were fed the HCO diet or chow. The results suggest that low dose supplementation of a mixture of n-3 (mainly 20:5n-3) and n-6 (18:3n-6) fatty acids modified both plasma TG content and liver delta 9 desaturase activity, in parallel.