[Subacute toxicity study of combination of adrenocorticotropine 1-13 and met-enkephalin]. / Studija subakutne toksicnosti kombinacije adrenokortikotropnog hormona 1-13 i metenkefalina.

PURPOSE: Combination FAR4 consists from two peptide components: met-enkephalin and alpha adrenocorticotropine 1-13 (ACTH 1-13) named before as alpha-melanocyte-stimulating hormone-like (alpha-MSH-like). Met-enkephalin and alpha-MSH exhibited cytoprotective effects individually and statistically significant additive effect was registered when both peptides were applied in combination on the model of ethanol induced gastric lesions in rats. We performed subacute toxicity study with subcutaneous application. WORK METHOD: Wistar rats were randomized in 3 test groups (treatments) consisted of 10 male and to female rats and one control group consisted of 20 male and 20 female rats. One daily dose was applied 3 days a week. Three dose ranges as multiplication of expected maximal human therapeutic dose (10 mg of met-enkephalin and 2 mg of alpha-ACTH 1-13) were estimated: equivalent dose, dose that was 5 times higher and 10 times higher dose. Animals were treated during 4 weeks with 10-days long observation period without the treatment after. After the planned scarification at the end of study, necropsy with histopathology examination was performed. RESULTS: No lethality, toxic signs or histopathological changes were observed during the subacute toxicity testing. Variation of laboratory animals body mass was observed through six terms of body mass deternimation. Increase in body mass was noted in all test and control groups. Statistical analysis with Kruskal Wallis single variance test showed statisticaly significant difference in the number of respirations between the groups of ma-. les for the first measurement (p = 0.040332) and second measurement (p = 0.016852), but multiple comparation with control group showed statisticaly significant difference. Afterthe planned scarification at the end of the study, necropsy did not reveal changes in macroscopic structure of organs and tissues. Histopathology examination was performed on the samples of liver, kidneys, lungs, heart, brain, spleen and thymus and no pathological changes were noted, while microscopic structure of tissues was perserved. The changes regarding postmortem organ mass as percentual ratio towards total group mass were not noted nor for males, nor for females. DISCUSSION: Study was conducted following the rules of the Guide for the Care and Use of Laboratory Animals made by the U.S. National Institutes of Health. Methodologicaly our study complys with rutine design of thistipe of studies. Subacute toxicity studies usually last for fourweeks and the way of test substance application to laboratory animals should comply to future way of application in human use. In our study no lethality was registered and low toxicity

Opiate-like peptides. Part XII. Synthesis and some biological properties of Met-enkephalin analogues modified in position 2 by D-alanyl residue in positions 2 and 4 by 3-(2-naphthyl)-D-alanyl residue.

Nine Met-enkephalin analogues containing D-alanyl residue in position 2 and/or 3-(2-naphthyl)-D-alanyl residue in positions 2 and 4 have been obtained. Their biological activity has been determined after intracerebroventricular administration to rats. Almost all compounds appeared strongly toxic causing the death of the animals. Only [D-2-Nal2,4, Met5-OMe]--enkephalin exerted an analgesic effect after the administration in the form of fine suspension.

Cardiovascular properties of metkephamid, a delta opioid receptor agonist, in man.

Opioid receptors exist in at least three forms: mu, delta and kappa. Agonists at mu receptors produce orthostatic hypotension in man by a mechanism involving a reduction in baroreflex sensitivity. We describe here the cardiovascular properties of metkephamid, a relatively selective delta opioid receptor agonist. Blood pressure, heart rate and plasma noradrenaline concentration were measured over a 7 h period in eight normal young male volunteers in the supine position and after 70 degrees 5 min head-up tilt, after receiving metkephamid (50 mg intramuscularly) or placebo. Metkephamid increased heart rate in the supine position with no change in blood pressure or plasma noradrenaline concentration. This was accompanied by symptoms consistent with an anti-muscarinic anticholinergic effect. Head-up tilt resulted in substantial hypotension after metkephamid with an attenuated change in heart rate and no increase in noradrenaline concentration. We conclude that delta as well as mu opioid receptor agonists can produce orthostatic hypotension with attenuation of heart rate response. Metkephamid possesses anticholinergic properties not seen with mu receptor agonists, suggesting a possible role of delta opioid receptors in cholinergic activity.

Opiate-like peptides. Part V. Aminoalkylamides of Met-enkephalin and [D-Ala]2-Met-enkephalin: synthesis and analgesic activity.

Four analogs of Met-enkephalin were synthetized using DPPA method. Their analgesic activity was estimated by the hot plate method, the neurotoxic effect being also determined. One of the analogs was 16 times as potent as Met-enkephalin, whereas with the three remaining the neurotoxic effect preceded the expected analgesic activity.

Human tolerability studies with D-Met2,Pro5-enkephalinamide.

As reported previously D-Met2,Pro5-enkephalinamide (EA) is a highly active enkephalin analogue. To examine its human tolerability male volunteers were treated s.c. with increasing doses (0.1-30.0 mg). The observed autonomic effects were as follows: feeling of heaviness in the limbs, dry mouth, pallor of the face and conjunctival injection. There was no significant change in blood pressure, pulse and respiratory frequency. The autonomic effects appeared within 15-30 min. However, its effects on mood and wakefulness i.e. slight drowsiness, decrease in psychic tension and emotional detachment developed only later. The serum prolactin level increased dose-dependently, while the growth hormone (HGH) content showed biphasic dose-response pattern. The TSH content increased only at the highest doses applied (10.0-30.0 mg).