Role of phosphatidylinositol-3-kinase and protein kinase Cζ in the adenylate cyclase signal mechanism of action of relaxin in muscle tissues of rats and mollusks

We showed that phosphatidylinositol-3-kinase and protein kinase C are involved in the adenylate cyclase signal mechanism of relaxin action. A selective inhibitor of phosphatidylinositol-3-kinase wortmannin blocked the stimulatory effect of relaxin on adenylate cyclase in rat skeletal muscles and Anodonta cygnea smooth muscles. Antibodies against protein kinase C abolished the relaxin-induced stimulation of adenylate cyclase in rat muscles, but not in mollusk muscles. Our results indicate that phosphatidylinositol-3-kinase and protein kinase C play a role in the adenylate cyclase signal mechanism of relaxin action.Translated from Byulleten Eksperimentalnoi Biologii i Meditsiny, Vol. 138, No. 10, pp. 420–423, October, 2004     

Synthesis and conformational analysis of the insulin‐like 4 gene product

Abstract: Insulin‐like 4 (INSL‐4) is a protein expressed in the early placenta. Its primary structure is insulin‐like with reference to the distribution of cysteine residues and the single chain pro‐form. Insulin‐like 4 was generated by solid‐phase peptide synthesis of the two chains followed by the sequential synthesis of the three disulfide bonds. Two disulfide isomers were produced, one with an insulin‐like disulfide bonding pattern and the other with a reversed chain orientation. The CD spectra of the two disulfide isomers were indistinguishable without any features produced by periodic structures. In addition, the hydrodynamic properties of the two isomers were identical which implied a very open structure of the disulfide‐bonded two‐chain molecules. It appears that insulin‐likeness cannot be defined solely on the basis of the primary structure of cDNA.     

增生后期及分泌期子宫内膜基质的超微结构

应用 TEM 及 SEM 观察人、猫及大鼠有关周期子宫内膜基质细胞的生长、发育和分化,并从细胞超微结构的动态变化进行分析。发现人子宫内膜在分泌早期,即出现少量前蜕膜细胞和颗粒细胞。至分泌后期,两种细胞数目剧增。颗粒细胞按其形态和结构特点,可分三型。Ⅰ型为圆形颗粒细胞,在人、猫及大鼠子宫内膜均可见到。Ⅱ型为大多边形颗粒细胞,见于人及猫的子宫内膜。Ⅰ型为梭形或细长形细胞,只见于大鼠。此外,并发现全部颗粒细胞和前蜕膜细胞均与胶原蛋白的合成密切相关。并讨论了颗粒细胞的来源、机能以及与前蜕膜细胞之间的相互关系。     

Interspecies Scaling of Clearance and Volume of Distribution Data for Five Therapeutic Proteins

The clearance and volume of distribution of five human proteins (recombinant CD4, CD4 immuno-globulin G, growth hormone, tissue-plasminogen activator, and relaxin) in humans and laboratory animals were analyzed as a function of body weight using allometric scaling techniques. These proteins cover a 16-fold range of molecular weight (6 to 98 kD), are produced by recombinant or synthetic methods, and may be cleared by different mechanisms. The analyses revealed that the clearance and volume data for each protein were satisfactorily described by an allometric equation (Y = a Wb). The allometric exponent (b) for clearance (ml/min) ranged from 0.65 to 0.84, the allometric exponent for the initial volume of distribution (ml) ranged from 0.83 to 1.05, and the allometric exponent for the volume of distribution at steady state (ml) ranged from 0.84 to 1.02. Exponent values from 0.6 to 0.8 for clearance and 0.8 to 1.0 for volumes are frequently cited for small molecules and are expected based on empirical interspecies relationships. When the preclinical data were analyzed separately, the pre-clinical allometric relationships were usually predictive of the human results. These findings indicate that the clearance and volume of distribution of select biomacromolecules follow well-defined, size-related physiologic relationships, and preclinical pharmacokinetic studies provide reasonable estimates of human disposition. Employing this methodology during the early phases of drug development may provide a more rational basis for dose selection in the clinical environment.     

Sex‐Specific Effects of Chronic Administration of Relaxin‐3 on Food Intake,Body Weight and the Hypothalamic‐Pituitary‐Gonadal Axis in Rats

The present study examined the effects of chronic central administration of relaxin‐3 (RLN3) on food intake, body weight and fat mass in intact and sterilised male and female rats, as well as on hypothalamic‐pituitary‐gonadal (HPG) axis activity in intact male and female rats that received i.c.v. infusions of RLN3 (400 pmol/day) or vehicle during a 14‐day period. The intact RLN3‐injected rats displayed a higher body weight than the vehicle‐treated groups, and this increase was statistically significantly stronger in female rats compared to male rats. In addition, feed efficiency and gonadal white adipose tissue weight were higher in female RLN3‐injected rats. Chronic i.c.v. administration of RLN3 activated the HPG axis in intact male rats, whereas inhibition of the HPG axis was observed in intact female rats. RLN3 significantly increased the plasma levels of luteinising hormone and follicular‐stimulating hormone in male rats but not in female rats. Conversely, hypothalamic expression of gonadotrophin‐releasing hormone mRNA was decreased by RLN3 in female rats but not in male rats. In addition, the plasma levels of oestradiol were significantly decreased by RLN3 administration in female rats. Consequently, intact RLN3‐injected female rats failed to display phasic inhibition of eating during oestrus. Sex‐specific effects of RLN3 on food intake and body weight were also observed in ovariectomised female and orchidectomised male rats, suggesting that the sex‐specific effects of RLN3 on energy metabolism are independent on the differential effects of RLN3 on HPG axis activity in male and female rats.     

Localization of relaxin‐3 in brain of Macaca fascicularis: Identification of a nucleus incertus in primate

Relaxin‐3 (RLN3) is a highly conserved, ancestral member of the insulin/relaxin peptide family. RLN3 mRNA is highly expressed in rat, mouse, and human brain and molecular genetic and pharmacological studies suggest that RLN3 is the cognate ligand for the relaxin family peptide‐3 receptor (RXFP3). The distribution of RLN3/RXFP3 networks has been determined in rat and mouse brain, but not in higher species. In this study we describe the distribution of RLN3 neurons in the brain of macaque (Macaca fascicularis) using in situ hybridization histochemistry and immunohistochemistry. RLN3 mRNA and high levels of RLN3‐like immunoreactivity (‐LI) were observed in neurons within a ventromedial region of the central gray of the pons and medulla that appears to represent the primate analog of the nucleus incertus (NI) described in lower species. Nerve fibers and terminals containing RLN3‐LI were observed throughout brain regions identical to those known to receive afferents from the NI in the rat, including the septum, hippocampus, entorhinal cortex, lateral, dorsomedial and ventromedial hypothalamus, supramammillary and interpeduncular nuclei, anterodorsal, paraventricular and reuniens thalamic nuclei, lateral habenula, central gray, and dorsal raphe, solitary tract, and ambiguus nuclei. Experimental studies in the rat strongly implicate a role of this neuropeptide‐receptor system in arousal, feeding, and metabolism, learning and memory, and central responses to psychological stressors. These new anatomical findings support the proposition that the RLN3 system is similarly involved in the integration and modulation of behavioral activation and arousal and responses to stress in nonhuman primates and humans. J. Comp. Neurol. 517:856–872, 2009. © 2009 Wiley‐Liss, Inc.     

The Structural and Functional Role of the B‐chain C‐terminal Arginine in the Relaxin‐3 Peptide Antagonist,R3(BΔ23‐27)R/I5

Relaxin‐3, a member of the insulin superfamily, is involved in regulating stress and feeding behavior. It is highly expressed in the brain and is the endogenous ligand for the receptor RXFP3. As relaxin‐3 also interacts with the relaxin receptor RXFP1, selective agonists and antagonists are crucial for studying the physiological function(s) of the relaxin‐3/RXFP3 pair. The analog R3(BΔ23‐27)R/I5, in which a C‐terminally truncated human relaxin‐3 (H3) B‐chain is combined with the INSL5 A‐chain, is a potent selective RXFP3 antagonist and has an Arg residue remaining on the B‐chain C‐terminus as a consequence of the recombinant protein production process. To investigate the role of this residue in the RXFP3 receptor binding and activation, the analogs R3(BΔ23‐27)R/I5 and R3(BΔ23‐27)R containing the B‐chain C‐terminal Arg as well as R3(BΔ23‐27)/I5 and R3(BΔ23‐27), both lacking the Arg, were chemically assembled and their secondary structure and receptor activity assessed. The peptides generally had a similar conformation but those with the extra Arg residue displayed a significantly increased affinity for the RXFP3. Interestingly, in contrast to R3(BΔ23‐27)R and R3(BΔ23‐27)R/I5, the peptide R3(BΔ23‐27) is a weak agonist. This suggests that the C‐terminal Arg, although increasing the affinity, alters the manner in which the peptide binds to the receptor and thereby prevents activation, giving R3(BΔ23‐27)R/I5 its potent antagonistic activity.     

The Janus face of maternal serum relaxin: a facilitator of birth,might it also induce preterm birth?

Objective: Preterm birth is a major cause of neonatal morbidity and mortality in the developed world. In order to better understand the pathophysiological pathway of this condition, the role of genetic factors and/or inflammation-associated molecules, as well as of socioeconomic parameters, is therefore under intense investigation. The purpose of this review study was to examine the potential role of maternal serum relaxin levels in the etiology of preterm birth.

Methods: Electronic databases (Pubmed, Embase, Cochrane Library) were searched for previously published research studies that investigated the biological role of relaxin and the mechanisms in which this hormone is involved during pregnancy and labor.

Results: It is evident that while relaxin is an essential endometrial/decidual angiogentic factor playing a vital role in maternal accommodation of pregnancy, elevated levels of this hormone could well be associated with preterm birth.

Conclusions: There are strong indications that maternal serum hyperrelaxinemia correlates with an increased risk of preterm birth.