Biomedical subjects

M N Ritta

Publications and source records attributed to M N Ritta.

22 records · Page 2Linked to original sources

PubMed1980

Effect of indomethacin on monoamine metabolism and melatonin synthesis in rat pineal gland.

Indomethacin treatment of rats resulted in a significant increase of pineal monoamine oxidase (MAO) type A activity, whereas it depressed MAO type B and hydroxyindole-O-methyl transferase activities. Indomethacin also significantly impaired the nocturnal rise of pineal serotonin-N-acetyltransferase activity and melatonin content. These results suggest a role for prostaglandins in the regulation of pineal function.

Acetylserotonin O-Methyltransferase↗

PubMed1979

Release and specific binding of prostaglandins in bovine pineal gland.

Incubated bovine pineal glands released prostaglandin E-and prostglandin F-like material (304 +/- 20 and 582 +/- 56 pg/mg dry tissue wt/h, respectively) and the release was increased 2.2 2.9-fold by adding 10(-4)-10(-6)M of norepinephrine to the medium. Binding assays revealed the existence of high affinity binding of 3H-prostaglandin E2 (3H-PGE2) and 3H-prostaglandin F1 alpha (3H-PGF2 alpha) in low speed supernatants of pineal homogenates. Binding was increased by increasing Ca++ concentration in medium up to 2 mM, was heat labile and was depressed following incubation with trypsin. In subcellular fractionation studies maximal 3H-PG binding was found in the 27000 x g pellet. Scatchard analysis of 3H-PGE2 binding revealed the presence of a single population of binding sites with a Kd= 1.2 nM and a binding site concentration of 1-2 pmoles/g protein. A single population of binding sites for 3H-PGF2 alpha was also detected with a Kd= 1.7 nM and a similar binding site concentration. Non-radioactive PGE1 and PGE2 were almost equally effective to compete for 3H-PGE1 binding sites (ED50= 5 and 2 nM, respectively). Unlabeled PGF1 was relatively ineffective to compete for 3H-PGE2 binding (ED50 greater than 1000 nM) but displaced effectively 3H-PGF2 alpha binding (ED20=1.2 nM).

Animals↗

PubMed1979

Fast axonal transport in rat sciatic nerve. Inhibition by pineal indoles.

The effect of pineal indoles on fast axoplasmic transport of proteins in the sciatic nerve was examined in rats injected with [3H]leucine in the sixth lumbar dorsal root ganglion. Melatonin (350-1100 nmol) applied locally in the sciatic nerve impaired significantly axonal transport. At a 350-nmol dose all other indoles tested (i.e., 5-hydroxyindoleacetic acid, 5-methoxyindoleacetic acid, serotonin, N-acetylserotonin, tryptamine, 5-methoxytryptamine) were less potent than melatonin to impair fast axonal flow. Vinblastine injected either into the ganglion or in the sciatic nerve markedly inhibited axonal transport.

5-Methoxytryptamine↗

PubMedDate not supplied

Catecholamine distribution in adult rat testis.

Catecholamine distribution in the adult rat testis was examined using a sensitive radioenzymatic method. Norepinephrine was present in the capsule and the interstitial fluid, in higher concentrations than dopamine, while in the interstitial cell preparations only norepinephrine was found. Epinephrine was undetectable in all testicular compartments investigated. No catecholamines were found in the seminiferous tubules. Testicular denervation caused a significant decrease in capsular catecholamines, confirming the neural origin of these amines.

Animals↗