Stimulation by proctolin of the ouabain-insensitive sodium efflux in single barnacle muscle fibers

Nwoga, Jude; Bittar, E. Edward

doi:10.1016/0742-8413(85)90018-0

Cited by 10 publications

(9 citation statements)

References 26 publications

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“…Stefani & Chiarandini, 1982), is able, when applied in a concentration of 2 mm, to completely block the stimulatory response of the ouabain-insensitive Na+ efflux to proctolin (Nwoga & Bittar, 1985). The results obtained with 2 mM-Cd2+ were as follows: 328 + 76 %, n = 4 vs. 616+71 % in controls, n=5 (P<005), and on repetition: 111+41%, n=4vs.…”

Section: The Effect Of Ca2+ Channel Blockerssupporting

confidence: 48%

“…Cobalt is also a known Ca2+ channel blocker (Stefani & Chiarandini, 1982), which when applied in a concentration of 10 mm completely abolishes the response of barnacle fibres to proctolin (Nwoga & Bittar, 1985). The results obtained here show that Co2+ fails to completely abolish the response to 10-5 M-PD (119 +9%, stimulation, n = 3 vs. 213 + 6 % in controls, P < 0 05); and upon repetition: 327+19%, n = 4 vs. 616 + 71 % in controls, n = 5 (P < 0 01).…”

Section: The Effect Of Ca2+ Channel Blockersmentioning

confidence: 99%

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A study of the ouabain‐insensitive sodium efflux in barnacle muscle fibres using phorbol dibutyrate as a probe.

Bittar

Nwoga

1990

The Journal of Physiology

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SUMMARY1. The resting ouabain-insensitive Na+ efflux in muscle fibres isolated from the barnacle, Balanus nubilus, is stimulated by external or internal application of phorbol 12,13-dibutyrate (PD). The response occurs fairly promptly and may not decay at all, or more commonly, decay rather slowly. The magnitude of the response to external or internal application of PD is dose-dependent, the minimum effective concentration being about 10-8 M.2. The response to PD fails to occur in the nominal absence of external Ca2+. Sudden removal of external Ca subsequent to peak stimulation by PD leads to almost complete reversal of the response. The response to PD of fibres suspended in Li+-ASW (artificial sea water) is similar in magnitude to that of fibres suspended in Na+-ASW. However, it differs in that it is of a sustained nature.3. Calcium channel blockers, e.g. verapamil, completely prevent the response to PD from occurring. Both Cd2+ and Co2+ are less effective than verapamil.4. Pre-but not post-injection of EGTA reduces the response to PD. Pre-or postinjection of Mg2+ reduces the response considerably.5. Fibres pre-injected with GTP show a reduced response to PD. Fibres preinjected with PD show a reduced response to GTP. Pre-injection of protein kinase inhibitor is without effect on the response to PD.6. Furosemide, piretanide and bumetanide are without effect on the response to PD. 7. DIDS (4,4'-diisothiocyanostilbene-2,2-disulphonic acid) is a potent inhibitor of the response to PD but not amiloride. Pyridoxal 5-phosphate and benzolamide are also powerful inhibitors. Pyridoxal 5-phosphate in combination with benzolamide fails to completely abolish or reverse the response to PD.8. Luminescence from aequorin is promptly increased by PD in a dose-dependent manner, the minimal effective concentration being in the nanomolar range. The signal is monophasic or multiphasic in shape, and is often less than 5 min in duration. Not infrequently, however, the aequorin response fails to completely decay and the new level of resting glow remains above the original baseline level.9. Collectively, these observations accord with a tentative general hypothesis stating that the stimulatory response of the ouabain-insensitive Na+ efflux to PD is triggered by two mechanisms. One involves a rise in myoplasmic free [Ca2+] resulting MS 7690 E2 E. BITTAR AND J. NWOGA from the entry of external Ca2+ via opened Ca2+ channels which is followed by the operation of the Na+{-Ca2+ exchanger in the reverse mode. The other involves stimulation of the Na+/HCO3--Cl-/H+ exchanger, presumably as the result of phosphorylation and/or an internal acidosis brought about by a sufficient rise in myoplasmic free [Ca2+].

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Section: The Effect Of Ca2+ Channel Blockerssupporting

confidence: 48%

Section: The Effect Of Ca2+ Channel Blockersmentioning

confidence: 99%

A study of the ouabain‐insensitive sodium efflux in barnacle muscle fibres using phorbol dibutyrate as a probe.

Bittar

Nwoga

1990

The Journal of Physiology

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“…The provisional conclusion that the external medium is the origin of trigger Ca2+ is supported by the experiments carried out with verapamil, Cd2+ and Co2+ (Nwoga & Bittar, 1985), high K+ and guanine nucleotides (Mason-Sharp & Bittar, 1981;Bittar & Nwoga, 1982 a, b). Such studies are obviously relevant to an understanding of so-called Ca2+-induced Ca2+ release.…”

Section: Discussionmentioning

confidence: 72%

“…As will be recalled, it is absolute in the case of the response of the Na+ efflux to proctolin (Nwoga & Bittar, 1985). Experiments were therefore performed in which Washington fibres pre-loaded with aequorin and pre-treated with 10-4 M-ouabain were suspended in nominally Ca2+-free ASW for 10-15 min prior to external application of 10-8 M-proctolin.…”

Section: Recording Of Aequorin Light Emissionmentioning

confidence: 99%

“…One reasonable but indirect way of approaching this problem is to obtain information by employing the barnacle muscle fibre as an experimental model. Thus, for example, the work of Nwoga & Bittar (1985) suggests that the neuropeptide proctolin stimulates the ouabaininsensitive Na+ efflux solely by a mechanism which involves activation of Ca2+ channels. This is indicated by evidence that the stimulatory response is abolished by Ca2± channel blockers, notably verapamil, Cd2+ and Co2+, and that it fails to occur in the nominal absence of external Ca2+.…”

Section: Introductionmentioning

confidence: 99%

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Further observations on the behaviour of ouabain‐insensitive sodium efflux towards proctolin in barnacle muscle fibres.

Bittar

Nwoga

1989

The Journal of Physiology

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SUMMARY1. A further study has been made of the stimulatory action of proctolin on the ouabain-insensitive Na+ efflux in single muscle fibres from the barnacle, Balanus nubilus.2. (i) Strontium (Sr2+) behaves as a substitute for external Ca2+. In this case, however, the response to proctolin fails to decay. (ii) Injection of Sr2+ stimulates the ouabain-insensitive Na+ efflux. This effect is mimicked by injecting Ca2 .3. Depolarization of the fibre membrane with 30 and 100 mM-external K+ augments the response to proctolin.4. Pre-injection of GTP or Gpp(NH)p (sodium 5'-guanylylimidodiphosphate) prevents the response to proctolin from completely decaying.5. Pre-injection of guanine nucleotides in conjunction with membrane depolarization stops the response to proctolin from decaying.6. Measurements of Em before and during treatment with proctolin indicate a prompt but small and reversible fall in the membrane potential.7. (i) The aequorin response of fibres pre-treated with ouabain to proctolin is monophasic or multiphasic, and concentration dependent, the minimal effective concentration being in the nanomolar range.(ii) The duration of these signals is usually less than 5 min; this is about half the time it takes for the stimulated Na+ efflux to reach a maximum. (iii) The aequorin response to proctolin occurs quite often in fibres suspended in nominally Ca2+-free artificial sea water. (iv) Sudden graded elevations in external K+ following complete decay of the aequorin response to proctolin are rapidly followed by stepwise transitory increments in light emission.(v) The aequorin response to 100 mM-external K+ is frequently a triplet. 8. (i) Together, these results are in line with the view that the action of proctolin on the ouabain-insensitive Na+ efflux is the result of a temporary fall in internal pCa and that its point of action is the Ca2+ channel, where a putative G protein in the presence of GTP or Gpp(NH)p is able to maintain constancy of the hormonal effect.(ii). They strengthen the argument that the barnacle muscle fibre as a preparation is especially suitable for studies of this kind.

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Invertebrate Endocrinology

Landau

Biggers

Laufer

1997

Comprehensive Physiology

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The sections in this article are: Growth and Morphogenetic Factors Insects Crustaceans Molluscs Other Invertebrates Regenerative Factors Crustaceans Insects Cnidarians Platyhelminths Annelids Echinoderms Others Pigmentary Factors Crustaceans Insects Osmoregulatory Factors Factors that May Increase Osmotic Pressure Factors that May Decrease Osmotic Pressure Metabolic Factors Biogenic Amines JHs and Farnesylacetone Adipokinetic Hormones and RPCH Crustacean Hyperglycemic Hormones Other Metabolic Factors Reproductive Factors Flatworms, Nemertines, and Nematodes Molluscs Crustaceans Insects Other Arthropods Annelids Echinoderms Behavioral Factors In Vitro Studies In Vivo Studies Pheromones Summary

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Stimulation by proctolin of the ouabain-insensitive sodium efflux in single barnacle muscle fibers

Cited by 10 publications

References 26 publications

A study of the ouabain‐insensitive sodium efflux in barnacle muscle fibres using phorbol dibutyrate as a probe.

A study of the ouabain‐insensitive sodium efflux in barnacle muscle fibres using phorbol dibutyrate as a probe.

Further observations on the behaviour of ouabain‐insensitive sodium efflux towards proctolin in barnacle muscle fibres.

Invertebrate Endocrinology

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