Effects of Acute Increases in Plasma Osmolality on Plasma Vasopressin-Associated Neurophysin in Conscious Rats: Implications for Osmoregulation

Cheng, Savio W.T.; North, William G.

doi:10.1159/000124099

Cited by 6 publications

(3 citation statements)

References 11 publications

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“…2). However, as observed in our previous study [6], the infusion did not produce a significant fall in plasma sodium concentration ([Na+ ]), or any significant changes in plasma vasopressin-associated neurophysin concentration ([VP-RNP]), MAP. or body weight.…”

Section: Le Raissupporting

confidence: 74%

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Responsiveness of Oxytocin-Producing Neurons to Acute Salt Loading in Rats: Comparisons with Vasopressin-Producing Neurons

Cheng¹,

North²

1986

Neuroendocrinology

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Plasma oxytocin-associated neurophysin concentration ([OT-RNP]) was used to evaluate the responsiveness of oxytocinergic neurons to an acute salt load in Long-Evans (LE) rats and Brattleboro homozygous (DI) rats. This responsiveness was compared with that of vasopressinergic neurons in LE rats as indexed by plasma vasopressin-associated neurophysin concentration ([VP-RNP]). Acute salt loading was induced by infusing 18% saline for 60 min into conscious, trained, chronically catheterized animals and plasma osmolality (P_osm) and mean arterial pressure (MAP) were monitored. An increase in P_osm was associated with a rise in [OT-RNP] and the relationship between Δ[OT-RNP] and ΔP_osm was similar for both LE and DI rats over the first 40 min of infusion (21.6 and 19.7 fmol ml^–1 mosm^–1 kg^–1, respectively). Although P_osm continued to rise between 40 and 60 min infusion, [OT-RNP] actually fell slightly during this period in LE rats to a final elevation of 682 ± 40 fmol/ml above initial values whereas [OT-RNP] in DI rats continued to rise to a final elevation of 1,927 ± 288 fmol/ml above initial values at 60 min of infusion. The differences between these elevations at 60 min for LE and DI rats were highly significant (p < 0.001). For LE rats, the increase of [OT-RNP] with P_osm for the first 40 min of infusion was much greater than the increase in [VP-RNP] with the slope between Δ[VP-RNP] and ΔP_osm being only 8.3 compared to 21.6 fmol ml"¹ mosm^–1 kg^–1 in the case of Δ[OT-RNP]. This difference was significant at p < 0.002. Of some additional interest was the unexpected finding that while MAP rose gradually with infusion of hypertonic saline in LE rats, it experienced a progressive decline during infusion in DI rats. The data obtained in this study indicate that oxytocin-producing neurons release more products than vasopressin-producing neurons in response to acute increases in P_osm. In addition, functioning vasopressin-producing neurons may, either directly or indirectly, have some negative feedback influence on the release of oxytocin at high plasma osmolalities (ΔP_osm between + 28 and + 40 mosm/kg FLO). Finally, the data on MAP imply that vasopressin-producing neurons may have a role in the hypertension that results from acute salt intake.

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Section: Le Raissupporting

confidence: 74%

“…Neurophysin re lease has been found to provide an excellent index of activ ity for vasopressinergic and oxytocinergic neurons [5,6,17,21].…”

Section: The Original Observations O F Jones and Pickering[\3]mentioning

confidence: 99%

Responsiveness of Oxytocin-Producing Neurons to Acute Salt Loading in Rats: Comparisons with Vasopressin-Producing Neurons

Cheng¹,

North²

1986

Neuroendocrinology

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“…For conscious rats, changes in plasma VP-RNP values by RIA are well correlated with changes in plasma osmolality (r = 0.73-0.78), have been used to successfully question the validity of the Verney hypothesis, and to show that vasopressin has a negative feedback influence on its own release. 28,29 Moreover, VP-HNP and VP-RNP, as reported for copeptin, are both stable against breakdown in plasma, for 24 h at ambient temperature, >48 hours at 4°C, and for at least 6 months at −20°C. 7,30,31 The apparent half-lives of neurophysins were found by us to be approximately one-and-one-half times those of vasopressin, and this is consistent with the findings of others.…”

Section: Discussionmentioning

confidence: 74%

Cancer and the Vasopressin Gene: Radioimmunoassay Values and Commentary on Copeptin as a Plasma Marker

North

2023

OTT

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Background: Vasopressin gene expression has been demonstrated to be a common feature of all small-cell lung cancer (SCLC) and breast cancer. Provasopressin (ProVP) is a component of the cancer cell membrane and a likely target for treatment. However, a measurable fraction of this cancer provasopressin is also normally processed and products are released into the circulation. Vasopressin (VP) and vasopressin-associated human neurophysin (VP-HNP), two of three products of processing, were earlier shown to be reliable plasma markers for determining the presence of SCLC and monitoring response to treatment. Material and Methods: In this study, copeptin, the third product of provasopressin processing, was preliminarily evaluated as a plasma marker for SCLC or breast cancer using radioimmunoassay (RIA). Antibodies directed against the 18 residue C-terminal peptide fragment of copeptin were used to avoid interference from the large-carbohydrate component of this endogenous glycopeptide. Results: The levels of copeptin in 8 male and 6 female patients with SCLC before treatment ranged from 16 to 319 pmol/L, and these levels were elevated (>2.5 times) in 10 of 14 cases (70%) when compared with healthy volunteers (normal mean, 18 ± 6 pmol/L). Volunteer values for males were smaller than for females (15± 4 pmol/L and 20± 9 pmol/L), but numbers were small. Patients with breast cancer had plasma levels ranging from 12 to 68 pmol/L, with only three of the six elevated. Conclusion: While cancer patients displayed a wide range of plasma copeptin levels over 70% with SCLC and 50% with breast cancer had clearly elevated levels. This finding indicates that for such patients, plasma copeptin, like plasma VP and VP-HNP, could be used to detect disease. The control values found for healthy volunteers using our RIA were in a range predictable from established normal plasma levels of both VP and VP-HNP.

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Acute infusion of lithium chloride raises blood pressure in the conscious rat

Cheng¹,

O'Connor²,

North³

1986

Neuropharmacology

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Effects of Acute Increases in Plasma Osmolality on Plasma Vasopressin-Associated Neurophysin in Conscious Rats: Implications for Osmoregulation

Cited by 6 publications

References 11 publications

Responsiveness of Oxytocin-Producing Neurons to Acute Salt Loading in Rats: Comparisons with Vasopressin-Producing Neurons

Responsiveness of Oxytocin-Producing Neurons to Acute Salt Loading in Rats: Comparisons with Vasopressin-Producing Neurons

Cancer and the Vasopressin Gene: Radioimmunoassay Values and Commentary on Copeptin as a Plasma Marker

Acute infusion of lithium chloride raises blood pressure in the conscious rat

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