Intracellular calcium and phospholipid turnover are not involved in the inhibition of iodothyronine 5'-deiodinase type II activity by T4

1991 ◽  
Vol 124 (1) ◽  
pp. 67-75
Author(s):  
Cristiana Juge-Aubry ◽  
Pierre Dôme ◽  
Catherine A. Siegrist-Kaiser ◽  
Alessandro M. Capponi ◽  
Albert G. Burger
Keyword(s):  
Intracellular Calcium ◽  
Calcium Concentration ◽  
Enzyme Inactivation ◽  
Free Calcium ◽  
Type Ii ◽  
Cytosolic Free Calcium ◽  
Experimental Conditions ◽  
Phospholipid Turnover ◽  
Free Calcium Concentration ◽  
Cytosolic Free Calcium Concentration

Abstract. In glial cell cultures, iodothyronine 5'-deiodinase type II is stimulated by dibutyryl cAMP. Serum-free medium increases enzyme activity and prolongs the half-life of the enzyme. T4 and rT3 specifically inhibit this activity. We tested whether enzyme inactivation by T4 was mediated by changes in cytosolic free calcium concentration and/or phospholipid turnover. Intracellular calcium concentration was decreased either by chelation of extracellular calcium or by chelation of extracellular and intracellular calcium. Neither basal hypothyroid 5'-deiodinase activity nor its inactivation by T4 were modified in such experimental conditions, compared with control cells incubated in normal calcium-containing medium. T4 by itself had no effect on the cytosolic free calcium concentration for up to 20 min. Studies on phospholipid turnover included norepinephrine in parallel to T4 as positive stimulation control. While norepinephrine clearly accelerated phosphoinositide turnover, there was no effect of T4 on any phospholipid turnover. These results suggest that neither cytosolic free calcium nor phospholipid turnover is involved in T4-dependent modulation of 5'-deiodinase type II activity in astrocytes in culture.

V2-like vasopressin receptor mobilizes intracellular Ca2+ in rat medullary collecting tubules

1993 ◽  
Vol 265 (1) ◽  
pp. F35-F45 ◽  
Author(s):  
A. Champigneulle ◽  
E. Siga ◽  
G. Vassent ◽  
M. Imbert-Teboul
Keyword(s):  
Intracellular Calcium ◽  
Calcium Concentration ◽  
Free Calcium ◽  
Cytosolic Free Calcium ◽  
Free Calcium Concentration ◽  
Cytosolic Free Calcium Concentration ◽  
The Mean ◽  
V2 Antagonist ◽  
Collecting Tubules ◽  
Calcium Pool

Cytosolic free calcium concentration ([Ca2+]i) was measured in single microdissected rat medullary collecting tubules [outer (OMCD) and inner (IMCD)] to identify receptors involved in vasopressin (AVP)-induced [Ca2+]i increases. In both segments, [Phe2,Orn8]vasotocin ([Phe2,Orn8]VT), a specific V1 agonist, as well as the V2 agonist 1-desamino-8-D-AVP (dDAVP) triggered [Ca2+]i variations. In OMCD, the mean response to 10 nM AVP roughly corresponded to the sum of V1 and V2 agonists effects. In IMCD, dDAVP (10 nM) alone reproduced the calcium response to AVP (delta[Ca2+]i = 243 +/- 34 nM, n = 6, and 248 +/- 27 nM, n = 8, with dDAVP and AVP, respectively). Furthermore, in the same experiments V1 and V2 maximal effects were not additive ([Phe2,Orn8]VT = 154 +/- 21 nM, n = 6; dDAVP + [Phe2,Orn8]VT = 233 +/- 23 nM, n = 9). As AVP, dDAVP released intracellular calcium (delta[Ca2+]i in calcium-free medium = 182 +/- 24 nM, n = 8, vs. 182 +/- 14 nM, n = 6 with 10 nM dDAVP and AVP, respectively). Neither 8-(4-chlorophenyl-thio)-adenosine 3',5'-cyclic monophosphate nor forskolin modified [Ca2+]i. A cross-reaction of dDAVP with an oxytocin (OT) receptor can be excluded since 1) the specific OT agonist [Thr4,Gly7]OT (10 nM) increased only slightly [Ca2+]i (delta-[Ca2+]i = 20 +/- 5 nM, n = 11); 2) the dDAVP response was not altered by the specific OT antagonist [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(O-methyl)tyrosine,4-threonine, 8-ornithine,9-tyrosylamide]vasotocin [d(CH2)5(1),O-Me-Tyr2,Thr4,Tyr-NH2(9)]OVT; 3) it was insensitive to V1 antagonists but was totally blocked by the V1/V2 antagonist [d(CH2)5(1),O-Et-Tyr2,Val4]AVP ([delta[Ca2+]i = 18 +/- 4 nM, n = 6). These results indicate that in IMCD AVP increases [Ca2+]i via both V1 and V2 receptors. [Ca2+]i variations due to V2 receptors involve a mechanism independent of adenylate cyclase and coupled to the same intracellular calcium pool as V1 and V2 receptors.

Angiotensin II causes sustained elevations in cytosolic calcium in glomerulosa cells

1988 ◽  
Vol 255 (3) ◽  
pp. E338-E346 ◽  
Author(s):  
R. E. Kramer
Keyword(s):  
Angiotensin Ii ◽  
Calcium Concentration ◽  
Cytosolic Calcium ◽  
Calcium Signal ◽  
Free Calcium ◽  
Cytosolic Free Calcium ◽  
Cytosolic Calcium Concentration ◽  
Free Calcium Concentration ◽  
Cytosolic Free Calcium Concentration ◽  
Glomerulosa Cells

Studies were conducted to examine the effects of angiotensin II on cytosolic free calcium concentration in bovine adrenal glomerulosa cells maintained in primary culture. The calcium indicator, fura-2, and discontinuous dual-wavelength fluorescence spectroscopy were used to measure cytosolic free calcium in superfused adherent cell monolayers. Basal cytosolic free calcium concentration was 63.7 +/- 3.3 nM. The threshold concentration for angiotensin II-stimulated increases in cytosolic calcium was 10(-14)-10(-13) M, and maximal elevation of cytosolic calcium was produced by 10(-9) M angiotensin II. Angiotensin II (10(-13) M) produced a gradual increase in cytosolic calcium concentration that plateaued after 3-5 min of superfusion at a level approximately 1.2 times that of control cells. The calcium signal invoked by a maximal concentration (10(-9) M) of angiotensin II, in contrast, was characterized by an immediate, intense (approximately 8-fold) increase in cytosolic calcium concentration that decayed within 5 min to a lower, but sustained, level 2.5-3 times that of control cells. The calcium signals invoked by intermediate concentrations (10(-12)-10(-10) M) of angiotensin II exhibited dose-dependent increases in magnitude and a gradual transition in nature between those invoked by threshold and maximal concentrations of the peptide. The effect of angiotensin II to increase cytosolic calcium concentration was accompanied by an increase in aldosterone output. The increase in steroidogenesis was most closely correlated with the magnitude of the initial calcium signal. At high concentrations (10(-10) and 10(-9) M) of angiotensin II, there was a clear dissociation between aldosterone output and the magnitude of the sustained calcium signal.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasopressin increases cytosolic free calcium in LLC-PK1 cells through a V1-receptor

1987 ◽  
Vol 253 (2) ◽  
pp. F328-F332 ◽  
Author(s):  
M. A. Burnatowska-Hledin ◽  
W. S. Spielman
Keyword(s):  
Parathyroid Hormone ◽  
Arginine Vasopressin ◽  
Calcium Concentration ◽  
Mdck Cells ◽  
Free Calcium ◽  
Base Line ◽  
Cytosolic Free Calcium ◽  
Free Calcium Concentration ◽  
Cytosolic Free Calcium Concentration ◽  
Dose Dependent

We examined the effects of arginine vasopressin (AVP), parathyroid hormone (PTH), and bradykinin (BK) on the cytosolic free calcium concentration ([Ca]i) in cultured LLC-PK1 and MDCK kidney cell lines by use of the fluorescent Ca chelator fura-2. In LLC-PK1 cells, the addition of AVP but not [1-desamino-8-D-arginine]vasopressin (dDAVP, V2 agonist), PTH, or BK (10(-6) M) caused a significant increase in [Ca]i. The AVP-induced increase in [Ca]i from 61 +/- 6 to 225 +/- 44 nM (n = 7, P less than 0.01) was rapid and transient, returning to base line in 2 to 3 min. The effect of AVP was dose dependent and was present at 1 (61% increase) but not 5 min after extracellular Ca was removed. The effect of 10(-6) M AVP could be blocked with the pressor (V1) antagonist, d(CH2)5Tyr(Me)AVP, but not dDAVP. In MDCK cells, BK, but not AVP and PTH, increased [Ca]i from 146 +/- 11 to 281 +/- 31 nM (n = 9, P less than 0.001). The removal of extracellular Ca (5 min), reduced but did not abolish this effect. These results indicate that [Ca]i mobilized by activation of V1-receptors may mediate AVP-regulated function in some transporting epithelia.

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