Investigation of the role and mechanism of effect of nucleotides on the isolated hearts of molluscs

S.-Rózsa, Katalin and Pécsi, Tibor (1968) Investigation of the role and mechanism of effect of nucleotides on the isolated hearts of molluscs. A Magyar Tudományos Akadémia Tihanyi Biológiai Kutatóintézetének évkönyve, 35. pp. 61-74. ISSN 0365-3005

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Abstract

1. All the four groujis of nucleotides investigated (adenine, guanine, uracil and cytosine) influence the functioning of the isolated Helix hearts. On Anodonta hearts cytosine nucleotides proved themselves to be ineffective. On the isolated Anodonta hearts the threshold concentration of the above nucleotides is 3040 times higher than on Helix hearts. 2. In the effects of adenine and cytosine nucleotides no seasonal changes appeared either on Helix or Anodonta hearts. Adenine nucleotides had a positive inotropic effect on Helix hearts with concentrations between 10⁻⁹-10⁻⁴ M and on Anodonta hearts with concentrations between 10⁻⁵-10⁻⁴ M, while with concentrations of 10⁻³-10⁻² M they produced a decrease in frequency and a systolic arrest on both hearts. Cytosine nucleotides on Helix hearts have a stimulatory effect up to a concentration of 10⁻² M, CDP being the most effective with a threshold concentration of 10⁻¹⁰ M. 3. Guanine and uracil nucleotides have different effects in spring and autumn on Helix hearts, but not on Anodonta hearts. This change in the effect is characteristic for nucleotides containing di- and triphosphates. CTP has a stimulatory effect in spring with concentrations of 10⁻⁷-10⁻² M, while the same concentrations lead to a complete inhibition in autum. UTP (10⁻⁹-10⁻² M) and UDP (10⁻⁸-10⁻² M) exert a reversed effect, i.e. inhibitory in spring and stimulatory in autumn. The seasonal changes can be connected to the change in types of metabolism before and after hibernation. On Anodonta hearts the guanine nucleotides proved to have an inhibitory effect (10⁻⁴-10⁻² M), while the uracil nucleotides have a stimulatory character (10⁻⁶-10⁻³ M). 4. The Helix hearts are protected by UDP and CDP against the stimulatory effect of 5-HT, while GTP, UTP and CTP transform it into an inhibitory one. Adenine nucleotides and those containing monophosphate are ineffective as regards modulation of the 5-HT effect. The CTP effect can be connected to the influence exerted on the 5-HT receptors of lipid nature, while the effect of UTP and GTP influencing the 5-HT effect should be connected with effects exerted on metabolic processes.

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