The effects of mercuric chloride on calmodulin-mediated Ca sup 2+ transport in rat brain

Journal Article · Mon Jan 01 04:00:00 EST 1990 · American Journal of the Medical Sciences; (USA)

DOI:https://doi.org/10.1097/00000441-199001000-00007· OSTI ID:6967454

Clifton, G G; Oelsner, D; Anderson, C R; Pearce, C J; Wallin, J D ^[1]

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1. Tulane Univ. School of Medicine, New Orleans, LA (USA)

We have shown previously that mercuric chloride (HgCl2) inhibits in vitro vasopressin release from the isolated rat neurohypophysis with maximum inhibition occurring with 0.5 mM HgCl2. Associated with the inhibition of hormone release is an increase in 45Ca+2 uptake, an increase in cytosolic 45Ca+2, and a reduction of 45Ca+2 accumulation by mitochondria in the intact gland. In the present series of studies, the effect of HgCl2 on calmodulin (CM) function in neural tissue preparations is reported. Mercuric chloride (0.5 mM) reduced 45Ca+2 binding to CM purified from bovine neurohypophyses by 20% and inhibited endogenous CM-stimulated Ca,Mg-ATPase activity from rat brain mitochondria in a dose-dependent fashion. Ca,Mg-ATPase activity was inhibited by 50 and 80% with 0.5 and 5.0 mM HgCl2, respectively. CM-stimulation of Ca,Mg-ATPase activity was inhibited by calmidazolium (CMZ) with maximal inhibition seen with 0.1 mM CMZ. Reversibility of the HgCl2 interaction with CM was demonstrated using CM-stimulated phosphodiesterase (PDEase) activity from rat brain. HgCl2 inhibited both basal and CM-stimulated PDEase activity in a dose-dependent manner with maximum inhibition occurring with 1.0 mM HgCl2. Preexposure of CM to an inhibitory concentration (1.0 mM) of HgCl2 resulted in no loss of stimulatory PDEase enzyme activity. From these results, we conclude that HgCl2 reversibly interferes with 45Ca+2 binding to CM and also inhibits CM-regulated Ca+2 pumping enzyme systems in the neurohypophysis. The inhibition of vasopressin release from the intact gland in the presence of HgCl2 thus, may be associated with a disruption of calcium in the neurohypophysis.

• OSTI ID: 6967454
• Journal Information: American Journal of the Medical Sciences; (USA), Journal Name: American Journal of the Medical Sciences; (USA) Vol. 299:1; ISSN AJMSA; ISSN 0002-9629
• Country of Publication: United States
• Language: English

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560300* -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ACID ANHYDRASES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
ATP-ASE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
BODY
BRAIN
CALCIUM 45
CALCIUM COMPOUNDS
CALCIUM ISOTOPES
CALMODULIN
CELL CONSTITUENTS
CENTRAL NERVOUS SYSTEM
CHLORIDES
CHLORINE COMPOUNDS
DAYS LIVING RADIOISOTOPES
DOSE-RESPONSE RELATIONSHIPS
ENZYME ACTIVITY
ENZYMES
ESTERASES
EVEN-ODD NUCLEI
HALIDES
HALOGEN COMPOUNDS
HYDROLASES
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
MAMMALS
MEMBRANE TRANSPORT
MERCURY CHLORIDES
MERCURY COMPOUNDS
MERCURY HALIDES
MITOCHONDRIA
NERVOUS SYSTEM
NUCLEI
ORGANIC COMPOUNDS
ORGANOIDS
ORGANS
PHOSPHODIESTERASES
PHOSPHOHYDROLASES
PROTEINS
RADIOISOTOPES
RATS
RODENTS
TRACER TECHNIQUES
VERTEBRATES