Cell cultures of neuroblasts from rat olfactory epithelium that show odorant responses

We have developed procedures that permit isolation and propagation of clonal cell cultures from the olfactory epithelium of the 5- to 7-day-old rat that appear to represent the neuroblasts that repopulate the sensory neurons in the olfactory epithelium throughout life. The cell lines we report here synthesize neuron-specific enolase, which is a neuron marker, 43-kDa growth-associated protein, a protein associated with neuronal growth cones, and carnosine, a possible olfactory neurotransmitter. In two of the cell lines we have found dose-dependent cAMP accumulation following exposure to submicromolar concentrations of chemical odorants in the medium. These two cell lines show different patterns of odorant specificity when tested against a panel of six chemicals commonly used as test odorants. We anticipate that these and similarly derived cell lines will prove valuable in studying aspects of neurogenesis and olfaction.

Cloned endothelial cells from fetal bovine bone

Primary cell cultures from fetal bovine sternum were developed in Coon's modified Ham's F-12 medium containing 10% Nu-Serum, 1% Ultroser-G, and 200 mg of galactose per liter. Clones were obtained by colony isolation; one clone, BBE-1, was selected for characterization. BBE-1 cells exhibited typical endothelial morphology by light and electron microscopy and immunofluorescence for factor VIII-related antigen throughout their life span of 8 months. The cells showed mitogenic responses to endothelial cell growth factor, basic fibroblast growth factor, insulin-like growth factor types I and II, platelet-derived growth factor, ascorbic acid, and progesterone. Parathyroid hormone stimulated intracellular accumulation of cAMP in BBE-1 cells but not in endothelial cells from two other tissues. These clonal cells provide a useful system for studies on bone vasculature, including its interactions with other bone cells.

Mitogenic activity on parathyroid cells in plasma from members of a large kindred with multiple endocrine neoplasia type 1

We tested plasma from 83 members of a large kindred with familial multiple endocrine neoplasia type 1 (FMEN1) for mitogenic activity on cultured bovine parathyroid cells. We evaluated the age dependency of parathyroid mitogenic activity (PMA) in plasma from affected and unaffected members of the kindred, and we analyzed the relation of plasma PMA to indices of activity of parathyroid, pancreatic islet, and anterior pituitary tissue. Plasma PMA was higher in members expressing the FMEN1 gene than in their unaffected first, second, third, or fourth degree relatives (P less than 0.05), and 10 of 20 members expressing the FMEN1 gene had plasma PMA above the 95% limit of the control range. Plasma PMA was not dependent on sex or age; the lack of age dependency and the high values in FMEN1 gene carriers suggested that plasma PMA is elevated in some FMEN1 gene carriers very early in life. Plasma PMA in known gene carriers varied significantly with one index of parathyroid function [plasma PMA was 2.5 times higher in the group with than in the group without prior parathyroidectomy (P less than 0.005), an indicator of more severe prior parathyroid disease] and correlated positively, although not significantly so, with indices of pancreatic islet function (serum gastrin by RIA) and anterior pituitary function (serum PRL by RIA). In summary, (1) plasma PMA levels are high in many known carriers of the FMEN1 gene, (2) the high plasma PMA levels in FMEN1 may precede overt endocrine hyperfunction; and (3) high plasma PMA levels vary with one index of parathyroid function, but do not correlate with indices of pancreatic islet or anterior pituitary function in members expressing the FMEN1 gene. The high plasma PMA levels in FMEN1 may be the direct cause of hyperfunction of the parathyroids, but the relation of high plasma PMA to hyperfunction of the pancreatic islets and anterior pituitary is uncertain.

Anti-endothelial cell antibodies: detection and characterization in sera from patients with autoimmune hypoparathyroidism

In a previous report, we described antibodies in autoimmune hypoparathyroidism (AHP) that are cytotoxic for cultured bovine parathyroid cells. In the present study, we show that sera from six AHP patients, but not from 26 patients with other autoimmune diseases or from 7 healthy subjects, react with bovine endothelial cells in culture (by flow cytometry and fluorescence microscopy) and in tissue sections (by immunohistology). We found uniformly that the immunoglobulin class reacting is IgM. Adsorption experiments showed that the antigenic determinants reacting with AHP sera were similar on bovine cultured endothelial cell membranes and in tissue sections of bovine parathyroid glands. The AHP sera also reacted with endothelial cells cultured from bovine adrenal medulla and pulmonary artery. Immunoblot analysis showed antibody binding to two major bands of 200 and 130 kDa solubilized from the membrane fraction of bovine parathyroid endothelial cells. Only one AHP serum consistently recognized endothelium-related structures on frozen sections of three different human parathyroid adenomas; two other sera reacted with one adenoma each; and three did not react with human adenomas. This indicates that human material is less suitable than bovine in detecting endothelium-related immune phenomena in AHP sera. The anti-endothelium IgM antibodies appear to be disease-specific but are not organ- or species-specific. The identification of endothelial cells as the target for antibodies in AHP raises the possibility that the endothelium subserves an important local function for endocrine epithelium.

Absent intestinal response to calciferols in hereditary resistance to 1,25-dihydroxyvitamin D: documentation and effective therapy with high dose intravenous calcium infusions

We describe a patient with an absent intestinal response to 1,25-dihydroxyvitamin D [1,25-(OH)2D] and the beneficial effects of treatment with high dose iv calcium infusion. The patient presented with severe rickets despite therapy with extraordinarily high doses of 1 alpha-hydroxyvitamin D3 or 1,25-(OH)2D3. Unidirectional intestinal fractional calcium absorption when he was not treated with any calciferol was 14% (normal, 20-70%), as measured with stable calcium isotopes; no increase in calcium absorption occurred when serum 1,25-(OH)2D levels were more than 50-fold elevated. Cultured skin fibroblasts contained no detectable 25-hydroxyvitamin D3-24-hydroxylase activity in response to 1,25-(OH)2D3 (10(-9)-10(-6) mol/L). High dose iv calcium infusions and oral phosphorus supplementation for 135 days improved or normalized biochemical parameters and resulted in radiographic healing of the rachitic lesions. We conclude that 1) this patient had no response to 1,25-(OH)2D3 in vivo and in vitro; 2) long term parenteral calcium infusions were effective therapy in managing the patient's severe resistance to 1,25-(OH)2D; and 3) stable calcium isotopes are useful for measuring low levels of fractional calcium absorption.

Insulin stimulates cell growth of a new strain of differentiated rat thyroid cells

A new strain, named WRT cells, has been generated from primary cultures of rat thyroids. The primary culture was grown in Coon's modified Ham's F12 medium with 5% calf serum, insulin, hydrocortisone, transferrin, somatostatin, glycyl-L-histidyl-L-lysine and thyrotropin (TSH). On the basis of the following facts, the WRT cell strain, cloned from the primary culture, was considered 'normal': the cells are euploid, not carcinogenic, not able to grow in soft agar, and show contact inhibition. Their differentiated functions consist of the ability to synthesize thyroglobulin and to take up iodide, and they have a TSH-dependent adenylate cyclase system. TSH increases cellular adenosine 3',5'-cyclic monophosphate (cAMP) levels and [3H]thymidine incorporation in WRT cells from a concentration similar to that active on another clonal rat cell line (FRTL-5), even though the cell replication appears to be differently regulated in the two cell strains. In fact, the WRT cell doubling time is 42 h and they are also able to grow in the absence of TSH, though more slowly. In the same conditions, FRTL-5 cells have a population doubling time of 38 h, but they are not able to grow in the absence of TSH. When the effect of the other growth factors of the medium was studied, insulin appears to be a growth stimulus by itself, while it is only a facilitative step for TSH action in FRTL-5 cells. WRT cells, unlike FRTL-5 cells, can grow with a population doubling time of 80 h, when cultured for prolonged periods in a medium with a low serum concentration (0.5%), but containing insulin plus TSH. In conclusion, the WRT cell strain is a new and interesting experimental model for studying growth factors at the level of the thyroid, especially for their mechanism of action on the TSH receptor.

Cholinergic control of cyclic nucleotide metabolism in human thyroid cells

In the presence of Ro 20-1724, a selective inhibitor of cyclic nucleotide phosphodiesterase, carbamylcholine increases cAMP and cGMP levels in human thyroid cells in primary culture. The increase of cAMP exhibited at concentrations of carbamylcholine between 10 fM and 10 pM, is dose- and time-dependent, it is maximum after 30 min and is abolished after 60 min. At higher carbamylcholine concentration (10 microM), cAMP increases rapidly, becoming maximum after 15 min, but returns to unstimulated values after 30 min. The increase of cGMP is also dose-dependent (0.1 nM-10 microM); it reaches the maximum after 30 min and returns to unstimulated values after 120 min. A significant increase of phosphodiesterase activity is observed at 10 microM carbamylcholine. Atropine, a muscarinic receptor antagonist, blocks carbamylcholine effects on both cAMP and cGMP production without affecting the thyrotropin-induced cAMP accumulation. Hexamethonium, a nicotinic receptor antagonist does not affect the cholinergic effects. In the presence of Ro 20-1724, 10 microM carbamylcholine significantly inhibits the effect of thyrotropin on cAMP production, while the combined addition of low doses of carbamylcholine and thyrotropin (0.1 nM and 10 pM, respectively) results in an additive effect on cAMP levels. Inhibition of thyrotropin activity on cAMP production, similar to that exerted by 10 microM carbamylcholine is produced by increasing free intracellular calcium; this inhibition is relieved by using a calmodulin-sensitive phosphodiesterase inhibitor, M and B 22948 at 50 microM dose. High concentrations (10 microM) of carbamylcholine increase the adenylate cyclase activity, without any significant effect on the thyrotropin-induced activation of the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction of VIPergic and cholinergic receptors in human thyroid cell

The thyroid tissue is innervated by cholinergic and VIPergic nerves. The present study investigated the possible interactions of cholinergic agents with VIP-induced cAMP accumulation and thyroid hormone release in vitro. Carbamylcholine (Cch), acting through the muscarinic receptor increases cellular cGMP content in cultured human thyroid cells incubated with a phosphodiesterase inhibitor. Cch (10 microM) inhibits cellular cAMP accumulation and thyroxine (T4) release induced by vasoactive intestinal peptide (VIP), with or without a phosphodiesterase inhibitor. Cch (10 microM) inhibits 8-bromo-cAMP-induced T4 release from human thyroid slices. 8-Bromo-cGMP inhibits VIP-induced T4 release from human thyroid slices, only in cells incubated without the phosphodiesterase inhibitor. The results indicate that interactions between VIPergic and cholinergic receptors may be of importance in human thyroid cell.

Functional epithelial cell line cloned from rat parathyroid glands

Primary cultures of rat parathyroid cells were developed in medium containing 5% calf serum, 1% Nutridoma-SP (a serum-free medium supplement from Boehringer Mannheim), and 0.7 mM calcium. The PT-r strain was purified by successive colony isolations and maintained differentiated characteristics (secretion of bioactive and radioimmunoactive parathyroid hormone into the culture medium, sensitivity to calcium regulation, and modulation by secretin) for 7 months in continuous culture. These cultured cells are epithelioid, display diploid chromosome numbers, and do not show a transformed phenotype. There has been no decrease in the rate of cell division or decline in parathyroid hormone secretion since the cell line was established. This clonal cell line provides an important system for further studies on the biology of the parathyroid cell.

Calcium-controlled secretion is effected through a guanine nucleotide regulatory protein in parathyroid cells

Calcium regulates parathyroid secretion through mechanisms yet to be elucidated. We have investigated this phenomenon through use of pertussis toxin which catalyzes ADP-ribosylation and inactivation of a guanine nucleotide regulatory protein, possibly Ni or No. Calcium inhibition of PTH release is blocked in cells treated with pertussis toxin, and there is concomitant ADP-ribosylation of a 40-kilodalton protein. The ionophore A23187 inhibits secretion in toxin-treated as well as in control cells. We conclude that a guanine nucleotide regulatory protein is involved in calcium regulation of PTH secretion at a locus proximal to the intracellular site effecting inhibition of secretion.

Antibodies cytotoxic to bovine parathyroid cells in autoimmune hypoparathyroidism

We utilized a recently developed long-term serum-free culture system for bovine parathyroid cells to detect antibodies in seven patients with autoimmune hypoparathyroidism (AHP). Antibodies were tested by indirect immunofluorescence methods and by cytotoxicity utilizing the chromium (51Cr) release technique. Seven AHP sera caused specific lysis [57 +/- 6% release of 51Cr vs. 5 +/- 1% for 56 controls (15 normal subjects and 41 patients with diverse other conditions associated with immune dysfunction)]. The least effect of any of the AHP sera on cell lysis exceeded the greatest effect of any of the control sera. Absorption of AHP sera (two cases) with bovine pituitary, thyroid, liver, or kidney cells did not affect lysis, but absorption with adrenal or parathyroid cells caused a marked decrease in specific lysis. Cytotoxicity determined by 51Cr release increased with antiserum concentration and time of incubation. Cytotoxicity was dependent on complement. Replicating parathyroid cells provide a uniform reproducible detection method for anti-parathyroid antibodies in AHP. The autoantibodies in AHP appear to be specific for tissue (parathyroid and adrenal cortex) but not for species.

Transient lack of response to TSH of human cultured thyroid cells obtained from hyperfunctioning tissue

TSH-induced cAMP accumulation in cells obtained from normal and pathological thyroid tissue was studied during the first 12 days of primary culture. In normal thyroid tissue cultures (N = 7), the response of cAMP to TSH was present from the second day of culture and reached its maximum after 8 days. A similar behaviour was observed in cultures obtained from euthyroid sporadic goitres (N = 8), even if the rate of response was slightly lower than that of normal tissue. Similarly, cultured cells from euthyroid 'autonomous' nodules (N = 8) appeared to be responsive to TSH during the period of study, but the rate of response was also lower than in the controls. On the contrary, in cultures obtained from toxic adenomas (N = 5) and from diffuse toxic goitres (N = 5) the response to TSH was absent during the first 4 days of culture. The cells became sensitive to TSH from 6 and 6 day onwards, with the rate of response increasing progressively and reaching its maximum on day 12. Finally, in cultured cells obtained from different areas of multinodular toxic goitres (N = 4), the response to TSH was similar to that of euthyroid goitres in cells prepared from 'cold' areas, and to that of toxic adenomas in cells obtained from 'hot' areas. The present data demonstrate the existence of an inhibitory action of unknown factors, possibly iodothyronines or thyroglobulin, on the TSH effect in short-term cultures obtained from thyrotoxic tissues. A normal TSH responsiveness can be restored when the culture is prolonged.

Control of PTH secretion is mediated through calcium channels and is blocked by pertussis toxin treatment of parathyroid cells

Parathyroid hormone secretion is negatively regulated by calcium. We utilized calcium channel agents: +202-791, a calcium channel agonist and -202-791, a calcium channel antagonist, to evaluate the role of calcium channels in PTH secretion. +202-791 inhibited PTH release from bovine parathyroid cells and the antagonist stimulated release. Incubation with pertussis toxin which ADP-ribosylates and inactivates a guanine nucleotide regulatory protein (G-protein) releases the inhibition by the calcium channel agonist. These findings indicate that a G-protein is interposed between the calcium channel and a putative intracellular site controlling PTH secretion.

Unusual antagonistic actions of mixtures of vasoactive intestinal peptide, thyroid-stimulating antibodies, and cholera toxin on adenosine 3',5'-monophosphate accumulation in normal human thyroid cell cultures

When individually tested, vasoactive intestinal peptide (VIP), cholera toxin, and monoclonal thyroid-stimulating antibodies (TSAbs), but not TSH binding-inhibiting antibodies (TBIAbs), elevate cAMP levels in cultured human thyroid cells. In this study, we tested the effect on cAMP levels in human thyroid cells of the simultaneous presence of VIP and the other ligands noted. Monoclonal TBIAbs (11E8 and 122G3), which interact with a membrane glycoprotein containing the high affinity binding site of the TSH receptor, did not alter VIP-induced cAMP accumulation in the thyroid cells. These data indicate that VIP and TSH bind to distinct sites on the cell membrane. In contrast, monoclonal TSAbs 208F7 and 307H6, which interact with a portion of the TSH receptor other than its high affinity binding site, not only did not have their usual agonist activity, but, instead, caused a marked inhibition of human thyroid cAMP accumulation when VIP was also present. Mutual antagonism by two agonists, i.e. inhibition evident when TSAbs and VIP were mixed, was also found when cholera toxin was coincubated with VIP. The inhibitory effect of mixing cholera toxin and VIP was nearly immediate and was duplicated with mixtures of the beta-subunit of cholera toxin and VIP. The inhibition evident in mixing VIP and the TSAbs or cholera toxin was not duplicated in mixtures of isoproterenol and VIP or in mixtures of forskolin and VIP. These results suggest that the mutual inhibition of VIP and either TSAbs or cholera toxin is at a step that couples the TSH and VIP high affinity receptor-binding sites to the adenylate cyclase complex.

Parathyroid mitogenic activity in plasma from patients with familial multiple endocrine neoplasia type 1

Hyperplasia of the parathyroid glands is a central feature of familial multiple endocrine neoplasia type 1. We used cultured bovine parathyroid cells to test for mitogenic activity in plasma from patients with this disorder. Normal plasma stimulated [3H]thymidine incorporation, on the average, to the same extent as it was stimulated in a plasma-free control culture. This contrasted with the results of the tests with plasma from patients with familial multiple endocrine neoplasia type 1, in which parathyroid mitogenic activity increased 2400 percent over the control value (P less than 0.001). Plasma from these patients also stimulated the proliferation of bovine parathyroid cells in culture, whereas plasma from normal subjects inhibited it. Parathyroid mitogenic activity in plasma from the patients with familial multiple endocrine neoplasia type 1 was greater than that in plasma from patients with various other disorders, including sporadic primary hyperparathyroidism (with adenoma, hyperplasia, or cancer of the parathyroid), sporadic primary hypergastrinemia, sporadic pituitary tumor, familial hypocalciuric hypercalcemia, and multiple endocrine neoplasia type 2 (P less than 0.05). Parathyroid mitogenic activity in the plasma of patients with familial multiple endocrine neoplasia type 1 persisted for up to four years after total parathyroidectomy. The plasma also had far more mitogenic activity in cultures of parathyroid cells than did optimal concentrations of known growth factors or of any parathyroid secretagogue. This mitogenic activity had an apparent molecular weight of 50,000 to 55,000. We conclude that primary hyperparathyroidism in familial multiple endocrine neoplasia type 1 may have a humoral cause.

Prostaglandin F2 alpha and alpha-adrenergic agonists regulate parathyroid cell function via the inhibitory guanine nucleotide regulatory protein

Prostaglandin F2 alpha (PGF2 alpha) and alpha-adrenergic agonists inhibit cAMP production and PTH secretion in dispersed bovine parathyroid cells. We have tested the mechanism of these effects utilizing pertussis toxin which catalyzes ADP ribosylation and inactivation of the inhibitory adenylate cyclase coupling protein Ni. Dispersed bovine parathyroid cells treated with or without 0.5 micrograms/ml pertussis toxin were tested with stimulatory (epinephrine, isoproterenol) or inhibitory (PGF2 alpha) agonists for responses in cAMP accumulation (5-min incubation) or PTH (90-min incubation) release. Pertussis toxin produced an enhanced response to epinephrine (a mixed alpha-adrenergic and beta-adrenergic agonist) in cAMP production and in PTH secretion. PGF2 alpha inhibited intracellular cAMP by 40% and PTH secretion by 35%. Pertussis toxin treatment of bovine parathyroid cells reduced the PGF2 alpha inhibition. We conclude that: 1) inhibition of PTH release by PGF2 alpha and alpha-adrenergic agonists parallels inhibition of cAMP production; 2) pertussis toxin blocks the inhibitory actions of PGF2 alpha and alpha-adrenergic agents on cAMP accumulation and PTH secretion; 3) the inhibitory coupling protein Ni mediates the inhibitory effects of these agents.

Bovine parathyroid cells: cultures maintained for more than 140 population doublings

Primary cultures of bovine parathyroid cells were developed using Coon's modified Ham's F-12 medium containing low (0.3 mM) concentrations of calcium and supplements of bovine hypothalamic extract, bovine pituitary extract, epidermal growth factor, insulin, transferrin, selenous acid, hydrocortisone, triiodothyronine, retinoic acid, and galactose. These cells were cultured serially on serum-coated dishes for 140 population doublings before signs of senescence were detected. The cells were epithelioid and maintained a high degree of differentiation as evidenced by calcium regulation of both growth and secretion and by prostaglandin E1 stimulation of cAMP formation and hormone release.

Loss of adrenergic regulation of cAMP production in the FRTL-5 cell line

Rat thyroid cells in primary culture augment cAMP production when challenged with beta-adrenergic agonists; at 10(-5) M the potency is isoproterenol greater than norepinephrine greater than epinephrine. In analogy with human thyroid cells, rat thyroid primary cultures display alpha-adrenergic-stimulated cGMP production which inhibits TSH and norepinephrine stimulation of cAMP. Adrenergic regulation of cyclic nucelotide production is lost in the cloned thyroid cell line of rat origin known as FRTL-5. Also the potentiating effect of phentolamine on TSH stimulation of cAMP production in thyroid primary culture becomes an inhibitory one in the FRTL-5 cells. Neither 'soluble factors' nor contamination of other cell populations could account for the different behaviour of the primary culture and the cell line toward adrenergic regulation. The reported activation by norepinephrine of iodide efflux in FRTL-5 cells rules out the loss of specific adrenergic receptors in the FRTL-5 cells. It is proposed that the cloning of FRTL-5 cells from primary cultures causes an 'alteration' in the coupling of adrenergic receptors to the adenylate cyclase system. This alteration does no affect those mechanism of message transduction that do not involve cAMP as the signal.

Catecholamine, vasoactive intestinal peptide and thyrotrophin-dependent cAMP levels display a different sensitivity to iodothyronines in both normal and pathological human thyroid cells in culture

As the interactions of iodothyronines on adrenergic and vipergic receptors are not clear, the effect of exogenous T3 and T4 on catecholamine- and VIP-induced cAMP accumulation in human normal thyroid cells after eight days of primary culture has been investigated. To evaluate the effect of endogenous iodothyronines, the response of the adenylate cyclase system to isoprenaline, adrenaline, VIP, and TSH was studied during a 10 d period. T3 and T4 were unable to modify the catecholamine- and VIP-induced cAMP accumulation in human normal thyroid cells after 6-8 days of culture, while the response to TSH was significantly inhibited. In cells cultured from thyrotoxic tissue, the response of the adenylate cyclase system to catecholamines and VIP, during a 10 d primary culture, showed a behaviour similar to controls. TSH responsiveness was negligible up to the fourth day of culture, while in normal cells a response to all the agonists was present from the beginning. In view of the lack of effect of iodothyronines on catecholamine- and VIP-induced cAMP accumulation, and of the superimposable behaviour of the response to catecholamines and VIP in normal and hyperthyroid cells during the first days of culture, we can conclude that iodothyronines do not directly modify the response of the adenylate cyclase system to adrenergic and vipergic stimulation in human thyroid follicular cells. The lack of responsiveness to TSH of cells obtained from hyperthyroid tissue during the first 4 d of culture, associated with normal responsiveness to catecholamines and VIP, points to a possible involvement of biogenic amines and neuropeptides in sustaining such hyperthyroid states.

Neuropeptidergic control of cyclic AMP accumulation in human thyroid cell

Somatostatin (SRIF), cholecystokinin (CCK), gastrin and substance P, as single agents, do not influence baseline cellular cAMP levels in human thyroid cultures. SRIF inhibits TSH-induced cAMP accumulation in human thyroid cell, while CCK, gastrin and substance P do not modify cAMP response to TSH. Vasoactive intestinal peptide (VIP) increases cellular cAMP levels in human thyroid cultures and its effect is additive to increases produced by norepinephrine (NE) and isoproterenol (ISO). Neither SRIF nor the other tested peptides influence adrenergic and VIP-ergic cAMP stimulation.

[Effect of laser irradiation on collagen production by fibroblasts in vitro]

The effects of the low power laser irradiation (Space Mix 5 Mid Laser) on the 3H-proline incorporation in the collagenic proteins produced by two lines of normal human fibroblasts in vitro were studied. The 3H-thymidine incorporation in cultures of control and irradiated fibroblasts of the same lines was also evaluated. The obtained results show that in the experimental conditions considered, laser irradiation may have a positive effect on the production of collagen by the fibroblasts in vitro. This effect is dependent on the time of exposure, the frequency of infra-red impulses and the age of subjects from which fibroblasts were obtained. The laser irradiation in the same experimental conditions does not affect the incorporation of 3H-thymidine in the fibroblasts in vitro. Therefore, the observed increase of collagen production is not dependent on an increase of cellular population.

Human calcitonin increases both cyclic AMP and cyclic GMP accumulation in human kidney cells

Salmon calcitonin stimulates both adenylate cyclase and guanylate cyclase systems in human kidney cortical cells but does not modify the cyclic nucleotide levels of medullary cells. In order to compare the effect of mammalian calcitonin and of calcitonin from the ultimobranchial body on cyclic nucleotides, the action of both salmon and human calcitonin was compared in intact kidney cells. The role of the regulatory unit in relation to the stimulation exerted by both calcitonins on the adenylate cyclase activity of kidney plasma membranes was also studied. Low concentrations of human calcitonin produced a significant increase of cyclic GMP accumulation in human kidney cortical cells. Higher hormone doses, active in stimulating the adenylate cyclase system, resulted in a progressive decline of the response. In kidney medullary cells human calcitonin was a more efficacious and potent stimulator of cyclic AMP than of cyclic GMP accumulation. Neither of the two calcitonins stimulated kidney cortical or medullary plasma membrane adenylate cyclase in the absence of guanylyl 5'-imidodiphosphate. However, in the presence of guanylyl 5'-imidodiphosphate, both calcitonins stimulated the cortical adenylate cyclase system. Under the same conditions, medullary adenylate cyclase activity was stimulated only by human calcitonin. These observations suggest that human calcitonin stimulates cyclic nucleotide accumulation in human kidney cortex and medulla, while salmon calcitonin is active only at the cortical level. This phenomenon could be explained on the basis of hormone-receptor binding.