<abstract xml:lang="en" xmlns="http://www.w3.org/1999/xhtml">The possible involvement of salivary gland extract (SGE) from horse flies in modifying hyperpolarization and relaxation via alterations in functional properties of sarcolemmal Na, K-ATPase in the host tissue was tested <italic>in vitro</italic> by application of various amounts of SGE from <italic>Hybomitra bimaculata</italic>.SGE in the amount of 3 μg proteins representing approximately the equivalent of one salivary gland of <italic>Hybomitra bimaculata</italic> induced a stimulatory effect on Na, K-ATPase at all ATP concentrations applied. This effect resulted from the improved ATP-binding site affinity in the Na, K-ATPase molecule, as implicated by the reduction in KM. Increasing the amount of SGE to 6.5 μg resulted in inhibition of the enzyme, which was characterized by reduction in Vmax and also KM. This suggests that in the presence of relatively high <italic>Hybomitra bimaculata</italic> SGE concentration some SGE components affect Na, K-ATPase, when ATP is already bound to the enzyme.Our results indicate that SGE from the horse fly <italic>Hybomitra bimaculata</italic> contain at least two different biologically active compounds modifying the acute recovery and maintenance of excitability during contractile activity in the host tissue by affecting Na, K-ATPase with opposite effects, depending on the ratio of SGE-proteins to proteins of the host tissue.</abstract>

The possible involvement of salivary gland extract (SGE) from horse flies in modifying hyperpolarization and relaxation via alterations in functional properties of sarcolemmal Na, K-ATPase in the host tissue was tested in vitro by application of various amounts of SGE from Hybomitra bimaculata.SGE in the amount of 3 μg proteins representing approximately the equivalent of one salivary gland of Hybomitra bimaculata induced a stimulatory effect on Na, K-ATPase at all ATP concentrations applied. This effect resulted from the improved ATP-binding site affinity in the Na, K-ATPase molecule, as implicated by the reduction in KM. Increasing the amount of SGE to 6.5 μg resulted in inhibition of the enzyme, which was characterized by reduction in Vmax and also KM. This suggests that in the presence of relatively high Hybomitra bimaculata SGE concentration some SGE components affect Na, K-ATPase, when ATP is already bound to the enzyme.Our results indicate that SGE from the horse fly Hybomitra bimaculata contain at least two different biologically active compounds modifying the acute recovery and maintenance of excitability during contractile activity in the host tissue by affecting Na, K-ATPase with opposite effects, depending on the ratio of SGE-proteins to proteins of the host tissue.

Effect of saliva from horse fly <italic>Hybomitra bimaculata</italic> on kinetic properties of Na, K-ATPase: possible role in regulation of relaxation

Institute for Heart Research, Department of Biochemistry, Slovak Academy of Sciences, Bratislava, Slovak Republic

Institute of Zoology, Slovak Academy of Sciences, Bratislava, Slovak Republic

Centre of Ecology and Hydrology NERC, Oxford, United Kingdom

Interdisciplinary Toxicology

Effect of saliva from horse fly  on kinetic properties of Na, K-ATPase: possible role in regulation of relaxation

The possible involvement of salivary gland extract (SGE) from horse flies in modifying hyperpolarization and relaxation via alterations in functional...

Effect of saliva from horse fly Hybomitra bimaculata on kinetic properties of Na, K-ATPase: possible role in regulation of relaxation

Published Online: Oct 24, 2011

Page range: 154 - 158

DOI: https://doi.org/10.2478/v10102-011-0024-8

Keywords
sodium pump, heart, horse fly, salivary glands

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