Synergistic effects of thyroxine and glucocorticoid in induction of trypsin-like esteroprotease in mouse submandibular gland

The granular convoluted tubule (GCT) cell of rodent submandibular glands

The granular convoluted tubule (GCT) is a segment of the duct system of all rodents, situated between the striated and intercalated ducts. It has the peculiar property of synthesizing a large variety of biologically active polypeptides whose role in saliva remains unknown. The literature on the fine structure of GCT cells is critically reviewed. Some recent developments on endocrine regulation of the structure and contents of rodent GCT cells are summarized, with emphasis on EGF, NGF, renin, and kallikrein proteases. A survey of the distribution of GCT cells in several vertebrate families is presented.

Kallikrein-like esteroprotease activity and kininase activity in submandibular gland from a mutant mouse with human cystic fibrosis like alterations

The submandibular gland of cri/cri and control mice were compared for their activity of glandular kallikrein like esteroprotease and kininase. Esteroprotease activity is significantly reduced in cri/cri mice with respect to control, with an increased kininase activity in cri/cri mice. Since previous work showed an electrolyte abnormality in the salivary glands of this mutant mouse (1) a possible relationship between this alteration with the low activity of cellular esteroprotease and the high kininase activity is suggested.

Regulation of functional mRNA levels for trypsin-like esteroproteases by 5 alpha-dihydrotestosterone and triiodothyronine in mouse submandibular salivary gland

The effects of 5 alpha-dihydrotestosterone and triiodothyronine on the levels of mRNA for trypsin-like esteroproteases in the submandibular glands of young female mice were examined using a translation system in a reticulocyte lysate. Immunoprecipitation of the trypsin-like esteroproteases synthesized in vitro gave almost the same isozyme profile as that of enzymes synthesized in vivo on isoelectric focusing in acrylamide gel containing 8 M urea. Although 5 alpha-dihydrotestosterone and triiodothyronine induced the enzyme activity 3-5 times, these hormones increased their functional mRNA levels only 45-70 per cent. These results suggest that there is little if any post-translational processing of esteroproteases and that hormones increase both the amount of mRNA and the efficacy of its translation.

Suppression by thyroid hormones of glucosamine-6-phosphate synthetase activity in rat sublingual glands

Thyroidectomy caused a significant increase in glucosamine-6-phosphate synthetase activity. Activity was returned to normal by injection of a physiological concentration of triiodothyronine. The results suggest that thyroid hormones regulate the activity of this enzyme in sublingual glands.

Basic isozymes of chymotrypsin-like esteroprotease from the mouse submandibular gland

Basic isozymes of chymotrypsin-like esteroprotease from mouse submandibular glands were purified 60-80-fold by a rather simple procedure consisting of CM-Sepharose CL6B chromatography and gel filtration on Sephadex G-100. The purified sample contained three major isozymes (A, B, C) and some minor ones. Their isoelectric points were between pH 10 and 11. The molecular weights of the main isozymes were estimated at 28000 by SDS-polyacrylamide gel electrophoresis. The acidic isozyme (A) separated into two polypeptide chains whose molecular weights were 21500 and 6500. Specific activities of these isozymes using Bz-Tyr-OEt as substrate were comparable to that of bovine pancreatic alpha-chymotrypsin, but they hydrolyzed casein 10 times slower than did alpha-chymotrypsin. The hydrolytic activities of these isozymes on Bz-Tyr-OEt were inhibited by diisopropylfluorophosphate, tosyl-L-phenylalanine chloromethyl ketone and chymostatin, but they were 400 times less sensitive to chymostatin than was alpha-chymotrypsin.

Sexual dimorphism of SDS peptide patterns from the submaxillary glands of mice

In mice (Mus musculus) sexual dimorphism is evident in the structure and function of the submaxillary glands, convoluted tubules being much more prominent in males than in females. Several enzymes are more abundant in the male gland. We have examined the submaxillary glands of male and female mice for the amounts of arginine peptidase and have made electrophoretic scans of SDS peptides in extracts of male and female glands during postnatal development and after androgen treatment. Larger peptides are relatively more abundant in female extracts, and smaller peptides are more abundant in the male extracts. The peptide patterns reflect the amount of arginine peptidase present in the extracts. No arginine peptidase could be detected in submaxillary salivary glands of mice from birth until 3 weeks of age. Then enzyme activity gradually increased, apparently induced by androgen hormones. The amounts of SDS peptides of high molecular weight steadily decreased with increasing age of the mouse and with increasing titers of arginine peptidase. Castration of the male led to the appearance of female SDS patterns; male patterns reappeared after treatment with testosterone. Females could be induced to form male patterns of SDS peptides by treatment with androgen hormones.

Postnatal development of trypsin-like esteroproteases in mouse submandibular gland

The development of trypsin-like esteroproteases in the submandibular gland of mice was studied, using a newly synthesized naphthyl ester (tosyl-L-lysine alpha-naphthyl ester) for the preparation of zymograms and for histochemical demonstration of the enzyme. Esteroprotease activities were first detected spectrophotometrically on day 15 after birth; then increased markedly after day 20. A sex difference in esteroprotease activity appeared on day 25. Zymograms prepared after isoelectric focusing in polyacrylamide slab gels showed that the glands of neonatal mice contained esteroproteases with a rather different composition from that of adult mice. The adult type isozymes appeared first on day 15, and their activities increased markedly after day 20. Histochemical studies revealed that the isozymes of neonatal mice were derived from mast cells. A few striated ducts were first stained on day 15, and the sex difference of the granular tubules became obvious on day 25. These results indicate that the development of trypsin-like esteroproteases faithfully reflects the differentiation of granular tubules in the mouse submandibular gland, except in the neonatal period.

Development of responsiveness of mouse submandibular gland to androgen and thyroid hormone

The effects of thyroxine and 5 alpha-dihydrotestosterone on the activities of various marker enzymes in the submandibular glands of immature mice were studied. The responsiveness to thyroid hormone appeared at latest by day five after birth, which was ten d earlier than the appearance of androgen responsiveness. The activity of trypsin-like esteroprotease, however, was not increased by these hormones until day 15 after birth.

Transplacental stimulation of lung development in the fetal rabbit by 3,5-dimethyl-3'-isopropyl-L-thyronine

The effect of thyroid hormone on maturation of fetal rabbit lung was studied with maternal treatment using 3,5-dimethyl-3'-isopropyl-L-thyronine (DIMIT), a synthetic analogue of triiodothyronine. To investigate the in vivo kinetics and distribution of DIMIT, we prepared [3H]DIMIT and injected both pregnant rats (18-21 d gestation) and rabbits (25 d gestation). In the rat, maximal concentrations of radioactivity in maternal plasma, fetal plasma, and amniotic fluid occurred within 10 min, 1-2 h, and 4-6 h, respectively, after intramuscular injection. After 7 h the concentration of radioactivity in fetal plasma was 163 and 71% of the maternal level in rats and rabbits, respectively, indicating that DIMIT readily crosses the placenta. We treated pregnant rabbits for 1-2 d with DIMIT in doses of 0.5-3 mg/kg per d and examined the fetuses at 26 and 27 d gestation. Treatment did not affect fetal growth or viability. In fetal liver, DIMIT increased the activity of NADPH cytochromeac reductase by 64% and decreased the glycogen content by 73% compared to controls. The rate of choline incorporation by lung minces increased in dose-dependent manner to a maximum of +104% at 3 mg/kg DIMIT; this does stimulated by 38% the activity of lung phosphatidic acid phosphatase (PAPase), a corticosteroid-responsive enzyme, but there was no increase in tissue PAPase activity at most lower doses of DIMIT that enhanced choline incorporation. Treated lungs had 38% less glycogen tha controls, but there was no effect on tissue levels of DNA, protein, or phospholipid. DIMIT treatment increased the amount of total phospholipid (+163%). saturated phosphatidylcholine (+330%), and PAPase activity (+134%) in lung lavage fluid. The DIMIT effects on both choline incorporation by lung minces and phospholipid content of lavage fluid were substantially greater than what had occurred with an optimal dose of betamethasone. DIMIT also increased corticosteroid binding capacity in fetal plasma and produced a dose-dependent increase (maximal threefold) in total and free corticoids of both maternal and fetal plasma. It is estimated that elevated endogenous corticoids probably account for less than one-third of the increases in phospholipid synthesis and secretion observed at the higher doses of DIMIT. These data indicate that administration of DIMIT to pregnant rabbits accelertes maturation of the surfactant system in fetal lung. The magnitude of the effects on phospholipid synthesis and secretion, along with the minimal effect of PAPase activity in fetal lung tissue, suggest that thyroid hormones affect different biochemical processes from those influenced by glucocorticoids.

Regulation of trypsin-like esteroprotease synthesis by 5 alpha-dihydrotestosterone and triiodothyronine in mouse submandibular gland

The hormonal regulation of trypsin-like esteroprotease synthesis in mouse submandibular gland was studied at the isozyme level. Antiserum to a mixture of two purified esteroproteases precipitated all the esteroproteases in a crude extract of this gland. Measurement of incorporation of [3H]leucine showed that total esteroprotease synthesis was stimulated by both 5 alpha-dihydrotestosterone and triiodothyronine and that the two hormones had synergistic effects. The observed correlation between the increases of synthetic rate and specific activity of this enzyme suggests that the enzyme level is regulated mainly by the rate of enzyme synthesis. Newly synthesized esteroprotease-antibody complexes gave four peaks of radioactivity with esteroprotease activity and one peak without enzyme activity on isoelectric focusing in acrylamide gel containing 8 M urea. The radioactivities of these five peaks were increased similarly by the two hormones separately or in a combination. These results suggest that the actions of androgens and thyroid homrones in esteroprotease synthesis are indistinguishable at the isozyme level.