184
A. M. PERKS
chromatography has separated a principle which appears to be arginine
vasotocin from a neutral peptide with the biological properties of oxytocin
(Pickering and McWatters, 1966). However, the authors point out that
8 Ile oxytocin might have been mixed with the oxytocin. Many of these
ambiguities result from the close similarity between the properties of
oxytocin and of 8 Ile oxytocin. It is possible that some individual biological assays might fail to make a clear distinction between them. For
this reason, the discrepancies which occurred during assays against
oxytocin standards carry the greatest weight in indicating the presence
of a peptide such as 8 Ile oxytocin. Similarly, the demonstration of discrepancies between an unknown and synthetic 8 Ile oxytocin, when they
were compared directly by different methods of biological assay, would
be better evidence for the presence of oxytocin-or some unknown
analog-in the lungfish extracts. However, many difficulties would be
resolved if the neutral peptides could be separated and analyzed by
chemical methods.
It appears probable that the lungfish share arginine vasotocin and 8 Ile
oxytocin with the amphibia. Even if they prove to possess oxytocin, this
cannot be regarded as an anomaly, since Munsick (1966) has suggested
that oxytocin occurs in at least one species of amphibian, Raw pipiens.
C. The Actions of Neurohypophysial Principles in the Dipnoi
Lungfish are not readily available to most investigators. Nevertheless,
their important position between the bony fish and the amphibians, which
appear to utilize their neurohypophysial principles in somewhat different
ways, has led to a surprising amount of work on the actions of the neurohypophysial principles in the metabolism of the dipnoans. However, the
work is confined almost entirely to studies of water and salt balance in
the African species, Protopterus aethiopicus.
There is no evidence that the injection of neurohypophysial principles
into the lungfish causes a water-balance effect analogous to that seen in
the frog. Large doses of oxytocin, or of a mammalian vasopressin preparation (2500 mU/100g body weight), or of pure arginine vasotocin (36
mpmoles/kg) had no effect on the total body water of free-swimming
specimens of Protopterus aethiopicus ( Heller, 1956; Heller and Bentley,
1%). Although it is possible that a water-balance effect might occur in
estivating specimens taken from the mud in the dry season, no studies
have been made at this time (Heller and Bentley, 1963). However,
present information suggests that the water absorption mechanisms of
the skin do not come under neurohypophysial control until the level of
A. M. PERKS
chromatography has separated a principle which appears to be arginine
vasotocin from a neutral peptide with the biological properties of oxytocin
(Pickering and McWatters, 1966). However, the authors point out that
8 Ile oxytocin might have been mixed with the oxytocin. Many of these
ambiguities result from the close similarity between the properties of
oxytocin and of 8 Ile oxytocin. It is possible that some individual biological assays might fail to make a clear distinction between them. For
this reason, the discrepancies which occurred during assays against
oxytocin standards carry the greatest weight in indicating the presence
of a peptide such as 8 Ile oxytocin. Similarly, the demonstration of discrepancies between an unknown and synthetic 8 Ile oxytocin, when they
were compared directly by different methods of biological assay, would
be better evidence for the presence of oxytocin-or some unknown
analog-in the lungfish extracts. However, many difficulties would be
resolved if the neutral peptides could be separated and analyzed by
chemical methods.
It appears probable that the lungfish share arginine vasotocin and 8 Ile
oxytocin with the amphibia. Even if they prove to possess oxytocin, this
cannot be regarded as an anomaly, since Munsick (1966) has suggested
that oxytocin occurs in at least one species of amphibian, Raw pipiens.
C. The Actions of Neurohypophysial Principles in the Dipnoi
Lungfish are not readily available to most investigators. Nevertheless,
their important position between the bony fish and the amphibians, which
appear to utilize their neurohypophysial principles in somewhat different
ways, has led to a surprising amount of work on the actions of the neurohypophysial principles in the metabolism of the dipnoans. However, the
work is confined almost entirely to studies of water and salt balance in
the African species, Protopterus aethiopicus.
There is no evidence that the injection of neurohypophysial principles
into the lungfish causes a water-balance effect analogous to that seen in
the frog. Large doses of oxytocin, or of a mammalian vasopressin preparation (2500 mU/100g body weight), or of pure arginine vasotocin (36
mpmoles/kg) had no effect on the total body water of free-swimming
specimens of Protopterus aethiopicus ( Heller, 1956; Heller and Bentley,
1%). Although it is possible that a water-balance effect might occur in
estivating specimens taken from the mud in the dry season, no studies
have been made at this time (Heller and Bentley, 1963). However,
present information suggests that the water absorption mechanisms of
the skin do not come under neurohypophysial control until the level of