Simultaneous measurement of atrial natriuretic polypeptide (ANP) messenger RNA and ANP in rat heart--evidence for a preferentially increased synthesis and secretion of ANP in left atrium of spontaneously hypertensive rats (SHR)

Tissue levels of atrial natriuretic polypeptide (ANP) messenger RNA (ANPmRNA) and ANP in the rat heart were measured simultaneously. In Wistar rats, ANPmRNA of the same size (approximately 0.95 kbp) was detected in all four chambers of the rat heart. The ANPmRNA level was the highest in the right atrium, and the left atrial level was slightly lower than the right atrial level. Ventricular levels were more than two orders of magnitude lower than atrial levels. Tissue ANP concentrations of four chambers were roughly parallel to ANPmRNA levels. In spontaneously hypertensive rats (SHR) with the elevated plasma ANP level, the ANPmRNA level in the left atrium was substantially increased. The left/right ratio of atrial ANPmRNA level in SHR (150%) was higher than that in control Wistar Kyoto rats (WKY) (90%). In contrast, the left/right ratio of atrial ANP concentration was decreased in SHR (44%) compared with that in WKY (84%). The ratio of ANP to ANPmRNA levels in the left atrium of SHR was about three times smaller than that in the right atrium of SHR, and those in bilateral atria of WKY. These results indicate that the biosynthesis and secretion of ANP from the left atrium is preferentially increased in SHR. Thus, simultaneous determination of ANPmRNA and ANP levels is a refined strategy of investigation for the biosynthesis, storage and secretion of ANP.     

High affinity binding of human interleukin 4 to cell lines

Purified human recombinant interleukin 4 (IL-4) was radio iodinated to high specific radioactivity without loss of biological activity. 125I-IL-4 bound specifically to the Burkitt lymphoma Jijoye cells and other cell lines. Jijoye cells showed a high affinity for 125I-IL-4 (Kd approximately equal to 7 10(-11) M) and displayed 1200-1400 specific receptors per cell at 4 degrees C or 37 degrees C. The equilibrium dissociation constant (Kd) corresponds to the IL-4 concentration which induces 50% maximal expression of the low affinity IgE receptor (Fc epsilon RL/CD23) on Jijoye cells. At 4 degrees C the rate constant of association K1 is 1.7 x 10(6) M-1 s-1 and the rate contant of dissociation k -1 is 1.3 x 10(-4) s-1 (t 1/2 = 91 min.) No human recombinant lymphokines other than IL-4 were able to compete for the binding of 125I-IL-4 to its receptor.     

A protein kinase C cDNA without the regulatory domain is active after transfection in vivo in the absence of phorbol ester.

We constructed mutant protein kinase C (PKC) cDNAs which expressed PKC activity in vivo in the absence of phorbol ester activation. A hybrid PKC gene, PKAC, was constructed by substituting the coding region for the N-terminal 253 amino acids of PKC alpha with the N-terminal 17 amino acids of the cyclic AMP-dependent protein kinase catalytic subunit (PKA). A truncated PKC gene, delta PKC beta, lacking the coding region for amino acid positions 6 to 159 of PKC beta was also constructed. These mutant kinase genes expressed under the control of the SR alpha promoter activated the c-fos gene enhancer in Jurkat cells and initiated maturation of Xenopus laevis oocytes. Phorbol ester binding activity was absent in both constructs but was preserved in another hybrid gene, PKCA, which was composed of the coding region for 1 to 253 amino acids of PKC alpha at the N-terminal side and the coding region for 18 to 350 amino acids of PKA at the C-terminal side. These results indicate that elimination of the regulatory domain of PKC produces constitutively active PKC that can bypass activation by the phorbol ester. delta PKC beta, in synergy with a calcium ionophore, was capable of activating the interleukin 2 promoter, indicating that cooperation of PKC-dependent and calcium-dependent pathways is necessary for activation of the interleukin 2 gene.     

Inhibition of rat ovarian 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), 17 alpha-hydroxylase and 17,20 lyase by progestins and danazol

The site of action of synthetic progestins or danazol in the treatment of endometriosis is considered to be mainly the hypothalamo-pituitary level, but the direct action to the uterine endometrium and the ovary is also suggested. We investigated the effect of these synthetic steroids to rat ovarian steroidogenic enzymes. The effect of norethisterone, levonorgestrel, danazol, gestrinone, desogestrel and 3-keto-desogestrel was studied in vitro. The sources of the enzymes were prepared from ovaries of immature rats treated either with pregnant mare serum gonadotropin (PMS) and human chorionic gonadotropin (hCG) for 3 beta-hydroxy steroid dehydrogenase (3 beta-HSD), or with PMS for 17 alpha-hydroxylase and 17,20 lyase. The substrates used were pregnenolone (P5) for 3 beta-HSD, progesterone (P4) for 17 alpha-hydroxylase, and 17 alpha-hydroxy-progesterone (17 alpha-OH-P4) for 17,20 lyase. The substrates were incubated with the enzyme sources and coenzymes, and the products formed were measured. All the steroids inhibited 3 beta-HSD, and the inhibition by gestrinone (Ki = 3.0 microM) and 3-keto-desogestrel (17.5 microM) was particularly marked. Only desogestrel (Ki = 30.3 microM) and danazol (168 microM) inhibited 17 alpha-hydroxylase. All the steroids inhibited 17,20 lyase, and the inhibition by desogestrel (Ki = 0.70 microM), danazol (0.80 microM), and gestrinone (30 microM) was particularly marked.     

Activation of boar proacrosin is effected by processing at both N- and C-terminal portions of the zymogen molecule

A mixture of 55 and 53 kDa boar proacrosins was autoactivated at pH 8.5 to produce a 43 kDa intermediate form and a 35 kDa mature acrosin, and each of four forms of (pro)acrosins was isolated. Analysis of the N-terminal sequences of the two proacrosins indicated the existence of a segment corresponding to the acrosin light chain at the N-terminal end of the zymogen. Two N-terminal sequences identical with those of the light and heavy chains were found in the intermediate form and mature acrosin. The proacrosins and the intermediate contained many more proline residues than the mature enzyme. These results indicate that the activation of boar acrosin zymogen is achieved by the removal of a C-terminal segment rich in proline residues and by the cleavage of the Arg23-Val24 bond leading to the formation of the light and heavy chains.     

Determination of the primary structure of Paim II, an alpha-amylase inhibitor from Streptomyces coruchorushii, by high-performance tandem mass spectrometry

This study indicates one of the advantages of tandem mass spectrometry; the primary structures of proteins with little structural difference can be determined by using tandem mass spectrometry without prior purification of each component. The primary structure of Paim II, a protein alpha-amylase inhibitor from Streptomyces coruchorushii, was determined by using tandem mass spectrometry. Paim II consists of two component proteins with ragged N-terminus, and was sequenced on the basis of the structure of Paim I, an analogous alpha-amylase inhibitor from the same natural origin.     

Isolation and sequence determination of rat cardiac natriuretic peptide

We have isolated a cardiac natriuretic peptide of 5K daltons from the rat atrium and determined its amino acid sequence. The 5K cardiac natriuretic peptide was elucidated to be a 45-amino acid peptide with the sequence of S-Q-D-S-A-F-R-I-Q-E-R-L-R-N-S-K-M-A-H-S-S-S-C-F-G-Q-K-I-D-R-I-G-A-V-S-R- L-G-C-D - G-L-R-L-F by sequencing the native peptide and its lysyl endopeptidase digests. The sequence of this peptide was identical to the amino acid sequence [51-95] of the rat brain natriuretic peptide (BNP) precursor deduced from the cDNA sequence. The 5K cardiac natriuretic peptide, or BNP[51-95], was identified as the major storage and secretory form derived from the BNP precursor in the rat heart.     

Endothelin in human plasma and culture medium of aortic endothelial cells--detection and characterization with radioimmunoassay using monoclonal antibody

We have developed monoclonal (KY-ET-1-I) and polyclonal (ET-F5) antibodies against endothelin-1 (ET-1) and established sensitive radioimmunoassays (RIAs) with different specificities. The RIA with KY-ET-1-I detected ET-1, ET-2 and ET-3, while the RIA with ET-F5 recognized ET-3 very weakly. Using these RIAs, we have investigated the concentration and molecular forms of ET-1-like immunoreactivity (-LI) in culture medium of bovine aortic endothelial cells and human plasma. Culture medium of endothelial cells contained two major components compatible with big ET and ET-1. ET-1-LI was also detected in human plasma. ET-1-LI in human plasma consisted of apparent two components, the small molecular form emerging at the position of ET-1 and the large form with the peak eluting at the preceding fraction of the elution position of big ET. The concentration of the small form of ET in human plasma was about 5 pg/ml.