Kallikrein-like prorenin-converting enzymes in inbred hypertensive mice

Kallikreins are a group of serine proteases and are distinguished by having serine residue at their active site. Their general function is to convert inactive pro-peptide into its biologically active form. In recent years, emerging evidence indicates that some kallikrein-kinin enzymes also play a role in the modulation of renin-angiotensin system. These kallikrein-like prorenin converting enzymes act on renin-angiotensin by converting prorenin into biologically active renin. In this investigation, kallikrein-like prorenin converting enzyme (PRCE C) (mK9) is isolated from genetically inbred high blood pressure (BPH) and their normal counterparts (BPN) mice, and its protein levels are quantitated. Levels of mRNA expression are also compared. Additionally, localization of the enzyme is visualized by in situ hybridization histochemistry. Results indicated higher levels of PRCE C (mK9) enzyme in BPH mice in comparison to their normal counterparts. mRNA expression was also higher in BPH mice. In situ hybridization histochemistry results localized PRCE C (mK9) in the striated duct cells of submandibular gland.     

In vitro and in vivo studies on the mechanism of experimental autoimmune thyroiditis in guinea pigs

Thyroid explants of inbred strain 13 guinea pigs were grown in a semisynthetic medium containing 0.3 IU of thyroid-stimulating hormone. The monolayer retained the capacity in vitro to form thyroglobulin. Sensitized lymphocytes from animals with autoimmune thyroiditis could specifically lyse these thyroid target cells in vitro in the presence of an appropriate amount of specific antigen. This cytotoxicity was not observed in thyroid epithelial cells which had been incubated (a) with normal lymphocytes or (b) with purified macrophages either from normal animals or from animals with autoimmune thyroiditis. When thyroid cells were incubated with hyperimmune antithyroglobulin serum, cytolysis did not occur, whether or not complement was added. The cytopathic effect of sensitized lymphocytes was further demonstrated to be caused by a soluble cellular product, termed thyroid cytotoxic factor, or TCF, which was released from sensitized lymphocytes under the stimulation of specific antigen, thyroglobulin, and could exert a cytotoxic effect directly on the target cells. Direct cell-to-cell contact was not required in this type of cell-mediated cytolysis.     

Immune response gene control of antibody specificity

The expression of the histocompatibility-linked PLL Ir gene was investigated in guinea pig B cells. Strain 2 and F₁ (2 × 13) guinea pigs, immunized with the αDnp-Lys₉, produce both T cells and antibody which are equally discriminatory for αDnp-Lys₉. In contrast strain 13 (PLL Ir gene negative) guinea pigs immunized with αDnp-Lys₉ do not develop specific T-cell responses and the antibody produced while restricted in heterogeneity cannot differentiate the immunizing antigen from Dnp-OH. However, if in a F₁ (2 × 13) environment, PLL Ir gene-negative B cells are provided with F₁ (2 × 13) T cells they express the ability to make antibody as specific and discriminatory as the antibody produced by PLL Ir gene-positive B cells. These findings strongly suggest that in the guinea pigs the PLL Ir gene defect is localized to the T cells and that the repertoire of specificity of B cells is similar if not identical in both responder and nonresponder animals. In addition these observations support the notion that the cellular locus for the PLL Ir gene expression in the guinea pigs is limited to T cells and not to macrophages and B lymphocytes.     

Androgen regulation of the cellular Distribution of the true tissue kallikrein mK1 in the submandibular gland of the mouse.

The kallikrein gene family encodes for at least four different proteases in the mouse submandibular gland (SMG): mK1 (true tissue kallikrein), mK9, mK13, and mK22. These enzymes and many other biologically active proteins are synthesized by the granular convoluted tubule (GCT), a specialized segment of the SMG duct system. The GCT is under multihormonal regulation by androgens, thyroid hormones, and adrenocortical hormones. Androgens suppress synthesis of mK1 in the SMG but enhance expression of the other three kallikreins. We prepared an antibody with limited immunoreactivity for mK1 and used it to examine the effects of androgen status on the distribution of this isozyme in the SMGs of developing and mature mice by immunoperoxidase staining for the light microscope and immunogold labeling for the electron microscope. In prepubertal mice, every immature GCT cell contains mK1, confined to an accumulation of small granules in the subluminal cytoplasm. In mature mice, not every GCT cell contains mK1, and in those cells that do there is considerable intergranular variation in the intensity of staining for mK1. GCT cells containing mK1 are much more abundant in the glands of females than of males, resulting in a peculiar sexually dimorphic mosaic distribution of this isozyme in the mature SMG. Castration of adult males increases the number of GCT cells expressing mK1. Administration of androgen to intact or castrated males or to intact females reduces the number of cells staining for mK1. In all cases, immunogold labeling for mK1 is confined to secretory granules. No fine structural differences were noted between cells that were positively or negatively stained for mK1. Therefore, although GCT cells appear to be composed of a uniform population of cells on the basis of morphology alone, they are not homogeneous in their content of secretory proteins. These results indicate that androgen regulation of GCT cells is more complex than has been appreciated to date.     

Differences in androgen-dependent induction of mk1, true tissue kallikrein in C3H/HeN and ICR mouse submandibular gland.

Androgen-dependent induction of mk1, true tissue kallikrein, in submandibular gland was studied in C3H/HeN and ICR mice and their F1 progeny. By injection of 5alpha-dihydrotestosterone (DHT), total esteroproteinase activities of female mice were increased to the level of male mice in both C3H/HeN and ICR strains. The mk1 content measured by the radioimmunoassay with anti-mk1 antiserum was decreased in ICR mice, but markedly increased in C3H/HeN mice after DHT injection. We examined the kallikrein isozyme pattern in SMG of two strains using isoelectric focusing. Female ICR mice expressed mainly mk1, mk13 and mk22, and slight mk9. Female C3H/HeN mice expressed mk1, mk9 and pI 6.6-kallikrein. Injection of DHT did not induce any additional kallikrein isozyme in C3H/HeN mice. Furthermore, we made an F1(C3H/HeN) mouse expressing mk13 and mk22 by mating (female C3H/HeN x male ICR). F1(C3H/HeN); these mice showed an androgen response similar to that observed in the ICR mice: mk1 induction in F1(C3H/HeN) mice was decreased by injection of DHT. We suggest the possibility that androgen-dependent mk1 biosynthesis might interact with the expression of other kallikrein isozymes.     

Substantial species differences in relation to formation and degradation of N-acyl-ethanolamine phospholipids in heart tissue: an enzyme activity study

The formation of N-acyl-ethanolamines (NAEs), including the cannabinoid receptor ligand anandamide, and their precursors N-acyl-ethanolamine phospholipids (NAPEs) are catalyzed by NAPE-hydrolyzing phospholipase D (NAPE-PLD) and N-acyl-transferase, respectively. NAPE and NAE are suggested to have beneficial effects on the heart, but in the literature there are indications of species differences in the activity of these enzymes. We have examined heart microsomes from rats, mice, guinea pigs, rabbits, frogs, cows, dogs, cats, mini pigs and human beings for activities of these two enzymes. N-Acyl-transferase activity was very high in dogs and cats (>13 pmol/min/mg protein) whereas it was very low to barely detectable in the other species (<3 pmol/min/mg protein). NAPE-PLD activity was very high in rats and guinea pigs (>45 pmol/min/mg protein) whereas it was 9 pmol/min/mg protein in frogs and below that in the other species. The ratio of activity between the two enzymes varied from 0.002 to 15 in the investigated species. The activity of the two enzymes in rat hearts as opposed to rat brain did not change during development. These results indicate that there may be substantial species differences in the generation of anandamide and other NAEs as well as NAPEs in heart tissues.     

Serological studies on the major histocompatibility complex of new inbred strains of the guinea pig.

New inbred strains of guinea pigs, JY 1, JY 2, JY 3, JY 6, JY 9 and JY 10 have been established in this Institute. Serologic studies of guinea pig leukocyte antigens (GPLA antigens) were carried out in order to examine their major histocompatibility complex (GPLA complex). Antisera specific for Ia antigens were raised by cross-immunization of NIH strain 2 (NIH 2) and NIH strain 13 (NIH 13) guinea pigs, well known inbred guinea pigs. The sera identified four distinct Ia specificities, which were designated as Ia.2a, Ia2b, Ia.13a and Ia.13b. Six antigenic specificities different from the above Ia specificities were identified by sera obtained by appropriate immunization of the inbred guinea pigs and were designated as P.1, P.2, P.3, P.4, P.5 and P.6. Antigenic specificities of GPLA antigens recognized in inbred guinea pigs were : NIH 2 (Ia.2a, Ia.2b, P.1, P.2, P.O, P.4), NIH 13 (Ia.13a, Ia.13b, P.1, P.2, P.3, P.4), JY 1 (Ia.13a, Ia.13b, P.5), JY 2 (Ia.2b, Ia.13b, P.3, P.4, P.6), JY 3 (Ia.13a, Ia.13b, P.2, P.4, P.5), JY 6 (Ia.2b, Ia.13b, P.3, P.6), JY 9 (Ia.13a, Ia.13b, P.4, P.5), JY 10 (Ia.13a, Ia.13b, P.2, P.3, P.4, P.6), JY 9 (Ia.13a, Ia.13b, P.4, P.5), JY 10 (Ia.13a, Ia.13b, P.2, P.3, P.4, P.6). The correspondence of these specificities to those already reported was discussed and the P.2 or P.4 was considered to be an additional specificity of GPLA antigens that have not been reported yet. As the new inbred strains of guinea pigs were thus found to possess characteristic GPLA complex, which differ from each other and from those of NIH 2 and NIH 13 strain, they should be useful for studies of roles of the major histocompatibility complex in the immune system.     

Unusual Ratio between Free Thyroxine and Free Triiodothyronine in a Long-Lived Mole-Rat Species with Bimodal Ageing

Ansell''s mole-rats (Fukomys anselli) are subterranean, long-lived rodents, which live in eusocial families, where the maximum lifespan of breeders is twice as long as that of non-breeders. Their metabolic rate is significantly lower than expected based on allometry, and their retinae show a high density of S-cone opsins. Both features may indicate naturally low thyroid hormone levels. In the present study, we sequenced several major components of the thyroid hormone pathways and analyzed free and total thyroxine and triiodothyronine in serum samples of breeding and non-breeding F. anselli to examine whether a) their thyroid hormone system shows any peculiarities on the genetic level, b) these animals have lower hormone levels compared to euthyroid rodents (rats and guinea pigs), and c) reproductive status, lifespan and free hormone levels are correlated. Genetic analyses confirmed that Ansell''s mole-rats have a conserved thyroid hormone system as known from other mammalian species. Interspecific comparisons revealed that free thyroxine levels of F. anselli were about ten times lower than of guinea pigs and rats, whereas the free triiodothyronine levels, the main biologically active form, did not differ significantly amongst species. The resulting fT4:fT3 ratio is unusual for a mammal and potentially represents a case of natural hypothyroxinemia. Comparisons with total thyroxine levels suggest that mole-rats seem to possess two distinct mechanisms that work hand in hand to downregulate fT4 levels reliably. We could not find any correlation between free hormone levels and reproductive status, gender or weight. Free thyroxine may slightly increase with age, based on sub-significant evidence. Hence, thyroid hormones do not seem to explain the different ageing rates of breeders and non-breeders. Further research is required to investigate the regulatory mechanisms responsible for the unusual proportion of free thyroxine and free triiodothyronine.     

Studies on the growth of the fetal guinea pig. Changes in plasma hormone concentration during normal and abnormal growth

The endocrine changes associated with fetal growth retardation caused by unilateral uterine artery ligation of guinea pigs at day 30 of pregnancy were studied. Plasma hormone levels in fetuses that, about 20 or 30 days later, were 35-50% of normal size were measured by radioimmunoassay. The small fetuses were severely hypoglycaemic and hypoinsulinaemic; both showing close correlation and relationship to the degree of growth retardation. Plasma thyroid and cortisol and concentrations were much lower than normal and that glucagon and androstenedione were much higher. Plasma growth hormone level appeared to be unaffected by growth retardation. The developmental changes in glucagon and thyroid hormone concentrations were consistent with a delay in the timing of prenatal events in growth-retarded fetuses. However the late cortisol rise, although somewhat blunted, still occurred at 58-60 in the small fetal guinea pigs.     

RNA extracts of lymphoid cells sensitized to DNP-oligolysines convert nonresponder lymphoid cells to responder cells which release migration inhibition factor

Strain 13 nonresponder peritoneal exudate cells were converted to responder status to α or ?,DNP-oligolysines after incubation of the cells with RNA extracts prepared from responder guinea pigs skin test sensitive to these synthetic antigens. The conversion of nonresponder strain 13 cells was assessed by the direct cell migration inhibition correlate of delayed hypersensitivity. Nonresponder cells were not converted by RNA extracts prepared from unimmunized responder guinea pigs or from non-responder strain 13 guinea pigs previously injected with DNP-oligolysines. Thus, it seems possible to correct immunological unresponsiveness in vitro in spite of a specific genetically determined deficiency of the immune response related to the Ir gene.     

Tissue kallikrein mK13 is a candidate processing enzyme for the precursor of interleukin-1beta in the submandibular gland of mice

By using Western blot analysis, high levels of 17.5- and 20-kDa interleukin-1beta (IL-1beta) proteins were detected in the submandibular gland (SMG) of mice. Despite this fact, the amount of pro-IL-1beta protein, a precursor of IL-1beta, with a molecular size of 35 kDa in this tissue was below the detectable level, although strong expression of pro-IL-1beta mRNA was observed. A large amount of 17.5-kDa IL-1beta also appeared in the saliva of mice injected with lipopolysaccharide, suggesting that this IL-1beta is a secretory form produced by the SMG. The protein for IL-1beta-converting enzyme, a processing enzyme for pro-IL-1beta, was expressed only at a low level in the SMG as compared with its level in various epithelial tissues or lipopolysaccharide-stimulated macrophages. On the other hand, mK1, mK9, mK13, and mK22, members of the kallikrein family, were detected strongly in the SMG but not in other tissues. By incubation with mK13, but not with mK1, mK9, or mK22, the 35-kDa pro-IL-1beta was cleaved into two major products with molecular masses of 17.5 and 22 kDa, and production was inhibited by phenylmethylsulfonyl fluoride, a serine protease inhibitor, but not by IL-1beta-converting enzyme inhibitors. A peptide segment corresponding to amino acid residues 107-121 of mouse pro-IL-1beta (107WDDDDNLLVCDVPIR) was cleaved by incubation with mK13, generating two peptides, 107WDDDDNL and 114LVCDVPIR. Therefore, kallikrein mK13 would appear to hydrolyze pro-IL-1beta between its Leu113 and Leu114 residues. The results of immunohistochemistry and an autonomic therapy experiment showed that IL-1beta and kallikrein mK13 were co-localized in the secretory granules of granular convoluted tubular cells. Our present results thus suggest kallikrein mK13 is a plausible candidate for the processing enzyme for pro-IL-1beta in the SMG of mice.     

Blood Biochemistry,Thyroid Hormones,and Oxidant/Antioxidant Status of Guinea Pigs Challenged with Sodium Arsenite or Arsenic Trioxide

The present experiment aimed to compare the two most commonly used compounds of arsenic (sodium arsenite and arsenic trioxide) for their effect on blood metabolites, thyroid hormones, and oxidant/antioxidant status in guinea pigs. Twenty-one adult guinea pigs were randomly divided into three equal groups. Animals in group T₁ (control) were fed a basal diet, whereas 50 ppm arsenic was added in the basal diet either as sodium arsenite (T₂) or arsenic trioxide (T₃) and fed for 11 weeks. Serum aspartate aminotransferase and alanine aminotransferase activities were significantly increased along with a decrease in blood hemoglobin level in both the arsenic-administered groups. The level of erythrocytic antioxidants (catalase, superoxide dismutase, reduced glutathione, glutathione-S-transferase, and glutathione reductase) was decreased and lipid peroxidation was elevated upon arsenic exposure. Serum thyroid hormone levels were reduced and arsenic levels in tissues increased in both the arsenic-exposed groups, irrespective of the arsenic compound. Thus, sodium arsenite and arsenic trioxide exerted similar adverse effects on blood metabolic profile, antioxidant status, and thyroid hormones in guinea pigs.     

Effect of prostaglandins in vivo on enzymes involved in thyroid carbohydrate metabolism.

Treatment of adult guinea pigs with prostaglandins produces changes in the levels of enzymes involved in carbohydrate metabolism of the thyroid gland. A decrease in glucose-6-phosphate dehydrogenase activity is observed with a concomitant increase in 6-phosphogluconic dehydrogenase; the glycolytic enzymes appear unaffected by the same treatment. The results indicate that prostaglandins do not have the biochemical effects obtained with thyrotropin and cAMP administration, showing that these compounds play an antagonistic role in comparison with the above mentioned stimulating agents.     

Morphochemical investigation of the thyroid gland of guinea pig in experimental acute anaphylactic shock

Some morphochemical changes were observed in the thyroid glands of guinea pigs in acute anaphylactic shocks (AAS). The growth of intensity of reactions for the enzymes of active transport was found. The vacuolisation of the cytoplasm of thyreocytes (as well as colloid) and numerous lesions of follicles were found together with the increase of activity of lysosomal enzymes. The changes of activity of oxidoreductive enzymes in ASS also presented and discussed.     

Alveolar macrophages in pulmonary immune responses. I. Role in the initiation of primary immune responses and in the selective recruitment of T lymphocytes to the lung

Antigen inoculated intratracheally (IT) into animals can induce primary immune responses and selectively recruit specific T cells to the lung. In the current study, the role of alveolar macrophages (AM) in these two responses was investigated. Antigen-pulsed bronchoalveolar cells (BAC) inoculated IT into guinea pigs generated a population of immune T cells that proliferated in vitro on reexposure to antigen-pulsed macrophages (M?). The possibility that antigen-pulsed donor BAC shed antigen that was subsequently processed and presented by host M? was ruled out by genetic experiments. Thus, peritoneal exudate lymphocytes (PEL) from (2 X 13)F1 guinea pigs primed with antigen-pulsed BAC from strain 2 animals responded preferentially to antigen-pulsed strain 2 M? rather than to antigen-pulsed strain 13 M?. In a second set of studies, antigen-pulsed BAC inoculated IT into guinea pigs selectively recruited antigen-specific T cells to the lung. Genetic experiments verified that inoculated BAC were the source of the antigen-presenting cells responsible for selective recruitment. Thus, antigen-pulsed strain 2 BAC inoculated IT recruited a greater proportion of (2 X 13)F1 T cells that recognized antigen in the context of strain 2 M? than F1 T cells that recognized antigen on strain 13 M?. Taken together, these studies suggest that AM contribute to the regulation of pulmonary immunity by both inducing T lymphocyte immunity and selectively recruiting specific T cells to the lung.     

Strain differences in susceptibility to experimental allergic encephalomyelitis and the immune response to the encephalitogenic determinant in inbred guinea pigs.

Strain differences in susceptibility to experimental allergic encephalomyelitis (EAE) in guinea pigs were correlated with the cellular immune response to the basic encephalitogenic protein (BE). The response to BE was determined in strains 2 and 13 guinea pigs in vivo by the delayed hypersensitivity skin test and in vitro by the lymphocyte transformation technique. The response to the intact BE of both heterologous (bovine) and homologous (guinea pig) origins was indistinguishable between the two strains. Guinea pigs sensitized with the guinea pig BE showed complete cross-reaction when tested with the bovine BE. On the other hand, there appears to be significant differences in the response to specific determinants on the molecule. Thus, only strain 13 and F₁ hybrids which are susceptible to EAE responded to the encephalitogenic nonapeptide (residue 114–122 of the BE molecule), whereas strain 2 guinea pigs which are resistant to EAE did not respond to this determinant.     

Enzymes of glycerolipid synthesis in small-intestinal mucosa of foetal and neonatal guinea pigs.

1. The activities of some enzymes of glycerolipid synthesis were measured in homogenates obtained from the intestinal scrapings of 62-66-day foetuses and 2- and 8-day-old guinea pigs. 2. The ratio of protein concentration/DNA concentration was significantly higher (P greater than 0.001) in homogenized tissue from the neonatal compared with the foetal guinea pigs. Enzyme activities were therefore expressed relative to both protein and to DNA. 3. The specific activities (relative to DNA) of palmitoyl-CoA synthetase, glycerol phosphate acyltransferase and phosphatidate phosphatase were higher in homogenized tissues from neonatal than in those from the foetal guinea pigs. These activities are probably involved more in cell proliferation than in the absorption and transport of triacylglycerol. Its activity was not significantly different in the foetal and neonatal guinea pigs when expressed relative to DNA but it was lower in the neonatal guinea pigs when expressed relative to protein. The entry of food into the intestine after birth is therefore not necessary for its activity.     

Triiodothyronine increases serum angiotensin converting enzyme

To determine whether elevated thyroid hormone is responsible for increased serum angiotensin converting enzyme in hyperthyroidism, 5 to 40 micrograms of 3,5,3'-triiodo-L-thyronine was administered orally and subcutaneously to female Swiss-Webster mice. Serum angiotensin converting enzyme was significantly increased in all animals given triiodothyronine compared to controls. Lung and kidney enzymes were moderately reduced in specific activity but unchanged in total activity due to increase in size of these organs. The results indicate that in hyperthyroidism, elevated thyroid hormone per se rather than the disease of the thyroid is responsible for elevated serum angiotensin converting enzyme.     

Uptake and retention of3H-estradiol by gonadotrophs and lactotrophs in the pituitary glands of the guinea pig,hamster and gerbil

Summary Nuclear uptake and retention of³H-estradiol by luteinizing hormone (LH) and prolactin (PRL) cells was examined in three species of rodents (guinea pigs, hamsters and gerbils) using the combined techniques of immunocyto-chemistry and autoradiography. Castrated animals were injected with³H-estradiol and decapitated 1.5 h later. The pituitary glands were processed for thaw-mount autoradiography followed by conventional immunocytochemical staining for LH and PRL.³H-estradiol accumulated in more than 80% of the anterior pituitary cells in the gerbils, while only 33 and 22% of the cells accumulated³H-estradiol in the hamsters and guinea pigs, respectively. A varying percentage of immunoreactive LH and PRL cells in all three species were found also to contain binding sites for estradiol. Some LH and PRL cells in hamsters and guinea pigs and only some in PRL cells of gerbils were found to be devoid of grains. Quantitative analysis revealed that the number of grains per nucleus differed considerably from cell to cell. LH cells of guinea pigs accumulated much larger amounts of³H-estradiol than did the PRL cells, while the LH cells in the hamsters and gerbils accumulated only slightly more³H-estradiol than the PRL cells.These results confirm the previous observations in rats and baboons that demonstrated tremendous species differences in percentage of cells in the anterior pituitary gland that accumulated³H-estradiol. Also, these data suggest that there are functionally heterogeneous cell types among the LH and PRL cells in hamsters, guinea pigs and gerbils as has been previously demonstrated in rats and baboons.     

The importance of thyroglobulin structure for thyroid hormone biosynthesis.

Thyroglobulin (Tg) is the most important protein in the thyroid because it provides the matrix for thyroid hormone biosynthesis. Here we review experimental work, principally from our laboratory, on the relationship between Tg structure and hormonogenesis. Early work showed that Tg's most important hormonogenic site was located in a fragment of approximately 26 kDa obtained on chemical reduction. With the establishment of the cDNA sequence of Tg, this and other major sites could be localized within Tg's polypeptide chain. The four major hormonogenic sites, designated A, B, C, and D, are located respectively at tyrosyls 5, 2553, 2746, and 1290. In most species, site A accounts for about 40% of Tg's hormone, and site B for about 25%. Site C is associated with increased T3, at least in some species. Site D is prominent in guinea pigs and rabbits, and TSH favors hormonogenesis at it in these species. Sequential iodination of low iodine human Tg shows three consensus sequences associated with early iodination and with T4 formation. Recent work has identified Tyr130 in beef Tg as donor of an outer iodothyronine ring, most likely to Tyr5, the most important hormonogenic site. In addition to its biochemical importance, Tg has clinical interest in familial goiter and autoimmune thyroid disease. Further elucidation of Tg structure and its relation to thyroid hormone synthesis will contribute to thyroid physiology and to its clinical application.