Summary
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1.
Gel filtration of tissue homogenates fromHelix aspersa separates cardioactive agents into four peaks of activity. One peak inhibits an isolated heart ofHelix, the remaining three are excitatory.
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2.
Elution characteristics, enzymatic sensitivity, and pharmacological properties indicate that the active principle of the inhibitory peak is acetylcholine, while that of one of the excitatory peaks is 5-hydroxy-tryptamine.
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3.
The two remaining peaks lose their activity when incubated with Pronase, trypsin, or chymotrypsin. This indicates that the active substances in these peaks are peptides.
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4.
The active substance of one of these peaks has an apparent molecular weight of ca. 700, and has been termed small cardioactive peptide(s) (SCP). Its presence is essentially confined to the nervous system and it does not appear to play a physiological role in control of the heart.
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5.
The other peptide cardioexcitor had an apparent molecular weight of ca. 7000, and was termed large cardioactive peptide(s), (LCP). It is found primarily in the sub-esophageal ganglia, several nerve trunks, the hemolymph, and in particularly high concentrations in the auricle.
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6.
Kinetic and pharmacological results suggest that LCP uses a different receptor in theHelix heart than does 5-HT.
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7.
It was concluded that LCP demonstrates several of the characteristics expected of a cardioactive neurohormone.
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Abbreviations
- LCP:
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large cardioactive peptide(s)
- SCP:
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small cardioactive peptide(s)
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I wish to thank Professors L.M. Riddiford, J.W. Truman, and A.O.D. Willows for critical reading of the manuscript. The research was supported by NSF grant BN575-13597A02 to A.O.D. Willows.
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Lloyd, P.E. Distribution and molecular characteristics of cardioactive peptides in the snail,Helix aspersa . J. Comp. Physiol. 128, 269–276 (1978). https://doi.org/10.1007/BF00656860
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DOI: https://doi.org/10.1007/BF00656860