Impact of nitric oxide on adrenomedullin- and proadrenomedullin N-terminal 20 peptide-induced cardiac responses: action by alone and combined administration

Adrenomedullin regulates sperm motility and oviductal ciliary beat via cyclic adenosine 5'-monophosphate/protein kinase A and nitric oxide

Cilium and flagellum beating are important in reproduction and defects in their motion are associated with ectopic pregnancy and infertility. Adrenomedullin (ADM) is a polypeptide present in the reproductive system. This report demonstrates a novel action of ADM in enhancing the flagellar/ciliary beating of human spermatozoa and rat oviductal ciliated cells. At the concentration found in the seminal plasma, it increases the progressive motility of spermatozoa. ADM binds to its classical receptor, calcitonin receptor-like receptor/receptor activity-modifying protein complex on spermatozoa. ADM treatment increases the protein kinase A activities, the cyclic adenosine monophosphate, and nitric oxide levels of spermatozoa and oviductal cells. Pharmacological activators and inhibitors confirmed that the ADM-induced flagella/ciliary beating was protein kinase A dependent. Whereas nitric oxide donors had no effect on sperm motility, they potentiated the motility-inducing action of protein kinase A activators, demonstrating for the first time the synergistic action of nitric oxide and protein kinase A signaling in flagellar/ciliary beating. The ADM-induced motility enhancement effect in spermatozoa also depended on the up-regulation of intracellular calcium, a known key regulator of sperm motility and ciliary beating. In conclusion, ADM is a common activator of flagellar/ciliary beating. The study provides a physiological basis on possible use of ADM as a fertility regulation drug.

Effect of adrenomedullin and proadrenomedullin N-terminal 20 peptide on sugar transport in the rat intestine

Previous studies have shown immunostaining of adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP) throughout the gastrointestinal tract. Based on these data, we decided to investigate the effect of these peptides on intestinal sugar absorption using everted rings from Wistar rat intestine. PAMP increases alpha-methylglucoside (MG) uptake at concentrations ranging from 10(-12) to 10(-7) M. AM shows a dual effect inhibiting sugar absorption at low concentrations (10(-12) to 10(-11) M) and increasing MG uptake at higher concentrations (10(-8) to 10(-6) M). In all cases, the effect is phloridzin-sensitive, indicating that the peptides alter SGLT1 function without modifying the non-mediated component of absorption. The enhancing effect of 10(-8) M AM and PAMP seems to be mediated by elevation of cAMP and is accompanied by an increase on SGLT1 expression in the brush-border membrane of the enterocytes. The inhibitory effect of 10(-12) M AM could be mediated by either cAMP reduction or, more probably, by other second messenger able to inhibit sugar absorption. PKC is not involved in the action of either AM or PAMP. These results demonstrate that both peptides play a role in the regulation of the active transport of sugars in the intestine.

Effects of peptides, with emphasis on feeding, pain, and behavior A 5-year (1999-2003) review of publications in Peptides

Novel effects of naturally occurring peptides are continuing to be discovered, and their mechanisms of actions as well as interactions with other substances, organs, and systems have been elucidated. Synthetic analogs may have actions similar or antagonistic to the endogenous peptides, and both the native peptides and analogs have potential as drugs or drug targets. The journal Peptides publishes many leading articles on the structure-activity relationship of peptides as well as outstanding reviews on some families of peptides. Complementary to the reviews, here we extract information from the original papers published during the past five years in Peptides (1999-2003) to summarize the effects of different classes of peptides, their modulation by other chemicals and various pathophysiological states, and the mechanisms by which the effects are exerted. Special attention is given to peptides related to feeding, pain, and other behaviors. By presenting in condensed form the effects of peptides which are essential for systems biology, we hope that this summary of existing knowledge will encourage additional novel research to be presented in Peptides.