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Met5-enkephalin-arg6-phe7 content of human and rabbit plasma
Abstract:
Using an adsorption technique combined with high pressure liquid chromatography and a specific radioimmunoassay, the met5-enkephalin-arg6-phe7 (YGGFMRF) content was measured in human and rabbit plasma. This heptapeptide content was 0.16 +/- 0.03, 0.20 +/- 0.05 pmol/10 ml plasma, for human and rabbit plasma, respectively. The degradation of YGGFMRF injected intravenously (rabbit) or that of the opioid heptapeptide added to rabbit plasma is rapid. The biological half life (T 1/2) of 125I-YGGFMRF in rabbit plasma was about 45 seconds (in vivo) and 1 minute and 8 seconds (in vitro). The metabolic clearance rate of YGGFMRF is slower than that of met5-enkephalin. The YGGFMRF content of rabbit plasma increased following inhibition of dipeptidyl peptidase activity by an intravenous injection of captopril. The presence of met5-enkephalin-arg6-phe7 into circulation indicates that it may have some physiological role, however it is unknown whether circulating YGGFMRF originates from adrenal medulla, intermediate lobe of pituitary or some other site.
Insights
The opioid heptapeptide met5-enkephalin-arg6-phe7 (YGGFMRF) is present in human and rabbit plasma. Its rapid degradation suggests a potential physiological role, though its origin remains unclear.
Area of Science:
- Biochemistry
- Pharmacology
- Endocrinology
Background:
- Opioid peptides play crucial roles in physiological processes.
- Met5-enkephalin-arg6-phe7 (YGGFMRF) is a heptapeptide with potential biological activity.
- Understanding the presence and fate of YGGFMRF in circulation is important.
Purpose of the Study:
- To quantify the content of met5-enkephalin-arg6-phe7 (YGGFMRF) in human and rabbit plasma.
- To investigate the degradation and metabolic clearance of YGGFMRF.
- To explore factors influencing YGGFMRF levels in plasma.
Main Methods:
- Adsorption technique
- High-performance liquid chromatography (HPLC)
- Radioimmunoassay (RIA)
- Intravenous injection and in vitro incubation studies
Main Results:
- YGGFMRF was detected in human (0.16 pmol/10 ml) and rabbit (0.20 pmol/10 ml) plasma.
- YGGFMRF undergoes rapid degradation in vivo and in vitro, with a short biological half-life (approx. 45 seconds in vivo).
- Metabolic clearance of YGGFMRF is slower than met5-enkephalin, and its plasma levels increase upon dipeptidyl peptidase inhibition with captopril.
Conclusions:
- The presence of YGGFMRF in circulation suggests a potential physiological role.
- Rapid degradation indicates tight regulation of YGGFMRF levels.
- Further research is needed to determine the origin and precise function of circulating YGGFMRF.