Values for ionized [Ca] in squid axons were obtained by measuring the light emission from a 0.1-mul drop of aequorin confined to plastic dialysis tube 140-mum diameter located axially. Ionized Ca had mean value 20 x 10(-9) M as judged subsequent introduction CaEGTA/EGTA buffer (ratio ca. 0.1) into axoplasm, and measurement on second drop. axoplasma was also measured introducing arsenazo dye an axon injection complex such multichannel spectrophotometry. so 50 calibrated against mixtures. Wth...

Nonenzymatic cytosolic fatty acid binding proteins (FABPs) are abundantly expressed in many animal tissues with high rates of metabolism. No physiological role has been demonstrated for any FABP, although these have implicated transport free long-chain acids (LCFAs) and protection against LCFA toxicity. We report here that mice lacking heart-type FABP (H-FABP) exhibit a severe defect peripheral (nonhepatic, non-fat) utilization. In mice, the heart is unable to efficiently take up plasma...

The membrane potential of frog sartorius muscle fibers in a Cl- and Na-free Ringer's solution when sucrose replaces NaCl is about the same as that normal solution. K+ efflux also two solutions but muscles lose K PO4 solutions. equal to given by Nernst equation for electrode, corrections are made activity coefficients inside outside fiber. For solution, measured within few millivolts EK. This finding incompatible with 1:1 coupled Na-K pump. It consistent either no coupling Na influx, or ratio...

A model is developed which requires the binding of 4 Na+ to a carrier before Ca site induced on opposite side membrane. Upon Ca, this translocates Na and Ca. The existence partially Na-loaded but nonmobile forms for (NaX, Na2X, Na3X) suffices explain both activating inhibitory effects transport reaction. Analytical expressions efflux influx in terms [Na]o, [Na]i, [Ca]o, [Ca]i, Em are Na/Ca exchange system at equilibrium; these provide quantitative description fluxes. Under nonequilibrium...

A method has been developed which allows a length of electrically excitable squid axon to be internally dialyzed against continuously flowing solution defined composition. Tests showed that diffusional exchange small molecules in the axoplasm surrounding dialysis tube occurred with half-time 2-5 min, and protein does not cross wall tube. The composition medium was (mM): K isethionate 151, aspartate taurine 275, MgCI(2) 4-10, NaCl 80, KCN 2, EDTA 0.1, ATP 5-10, phosphoarginine 0-10. following...

The effects which alterations in the concentrations of internal sodium and high energy phosphate compounds had on influx efflux internally dialyzed squid axons were examined. Nine naturally occurring ineffective supporting significant extrusion. These were: AcP, PEP, G-3-P, ADP, AMP, GTP, CTP, PA, UTP.(1) compound d-ATP supported 25-50% normal extrusion, while ATP 80-100%. relation between was nonlinear, rising most steeply range 1 to 10 microM more gradually 10,000 microM. There no evidence...

Squid giant axons were internally dialyzed with a medium free of metabolic substrates but containing 45Ca buffered EGTA to concentrations Ca++ in the range 0.01-230 muM. At (Ca)i 1.0 muM OR GREATER, Ca efflux was 1-3 pmol/cm2 s, dependent on (Na)o and (Ca)o, sensitive membrane potential. lower (Ca)i, sensitivity potential greater. Hyperpolarization increased, depolarization decreased over potentials studied (-20 -100 mV). The maximum order an e-fold increase for 25-mV Em; this lost if...

Measurements have been made of K influx in squid giant axons under internal solute control by dialysis. With [ATP](i) = 1 microM, [Na](i) 0, was 6 +/- 0.6 pmole/cm(2) sec; an increase to 4 mM gave 8 0.5 sec, while 4, 80 a 19 0.7 sec (all measurements at approximately 16 degrees C). Strophanthidin (10 microM) seawater quantitatively abolished the ATP-dependent influx. The concentration dependence on [ATP](i), [Na](i), and [K](o) measured; 30 microM about half that physiological concentrations...

Measurements have been made of the fluxes thallous ions (Tl(+)) across membrane frog sartorius muscle fibers. These show that at an external concentration 74 microM influx is about 270 x 10(-15) moles/cm.(2) sec., while efflux from a with internal equal to above 5 sec. The increased order 300-fold during twitch, and Tl(+) reach steady-state distribution between fiber water Ringer solution very close corresponding ratio for K(+). High concentrations depolarize 58 mv. tenfold increase in...

The membrane of the squid axon is considered on basis a pore model in which distribution sizes strongly favors K(+) transfer when there no potential. Electrical asymmetry causes non-penetrating ions capacitor to exert mechanical force both surfaces and this results deformation system such that it assumes favoring exerting force. involved appear be Ca(++) outside isethionate(-), (i(-)) inside; as equivalent size Na(+), charged potentially able deforming are removed. A depolarization leads an...

A B S TRA C T Changes in ionized calcium were studied axons isolated from living squid by measuring absorbance of the Ca binding dye Arsenazo III using multiwavelength differential absorption spectroscopy.Absorption changes measured situ calibrated vitro with media ionic composition similar to axoplasm containing CaEGTA buffers.Calcium loads 50-2,500 /zmol/kg induced microinjection, stimulation 112 mM seawater, or soaking choline saline 1-10 Ca.Over this range loading intact axoplasm, rose...

Frog sartorius muscles subjected to overnight loading with Na(+) in K-free Ringer the cold were subsequently labeled Na(24) and then immersed choline efflux of followed for 4 hours. The initial appeared be 17 pmole/cm(2) sec.; this value was maintained 20 minutes by an abrupt decline about 9 sec. This latter rate next efflux. declined gradually time reached values order 0.1 back addition counts lost from enabled one calculate relationship between [Na](i) muscle. roughly approximates S-shaped...

The influx of Na+, K+, Rb+, and Cs+ into frog sartorius muscle has been followed. results show that a maximum rate is found for while Na+ penetrate much more slowly. Similar measurements with Ca++, Ba++, Ra++ Ba++ penetrates at somewhat greater than either Ca++ or Ra++. All these divalent cations, however, rates slower do the alkali cations. obtained are discussed reference to model developed explain different penetration

Frog sartorius muscles were made Na-rich by immersion in K-free sulfate Ringer's solution the cold. The then loaded with Na(24) and extracellular space cleared of radioactivity. When such transferred to lithium at 20 degrees C, Na efflux was observed increase time, reach a maximum about 15 minutes after transfer Li(2)SO(4), decline. decline from these proportional ([Na](i))(8) over considerable range [Na](i). membrane potential -48 mv 4 C but changed -76 same -98 Li(2)SO(4) C. By contrast,...

Squid giant axons were internally dialyzed by a technique previously described. In an axon exposed to cyanide seawater for 1 hr and with ATP-free medium, the Na efflux had mean value of 1.3 pmole/cm(2)sec when [Na](i) was 88 mM, in quantitative agreement flux ratio calculations purely passive movement. When ATP at concentration 5-10 mM supplied axoplasm dialysis, rose almost 30-fold, while if phosphoarginine, 10 instead ATP, only about 15-fold. The substitution Li outside did not affect from...

It is possible to develop a method of analyzing membrane pore sizes based on quite different principles from those so elegantly described by Dr. Solomon in this Symposium. This depends upon an assumption that ions aqueous solution will not penetrate through with pores less than I o A radius unless the size ion and are almost equal (1). Such situation makes it equate permeability for number just fit particular size. The conclusion such analysis mean excitable membranes about 4.0 A; value...