Electrical activity of the canine liver

Preliminary

ELECTRICAL

ACTIVITY

M. STEPHEN

R.

SANKARAN TOPAZ,

OF

VALIATHAN, B.S.,

AND

of the electrical activity of liver cells has been of relatively recent interest. Beigelman et al. [I] reported electrical potentials as high as 45 mv. in viable adult rat and chick embryo hepatic tissue; these potentials, however, declined progressively with tissue autolysis. The apparatus employed in their study consisted essentially of silver chloride electrodes, glass microelectrodes for direct insertion into the tissues, and a suitable recording device. In preliminary in vivo studies with rat liver in situ, they observed DC potentials of 50 to 60 mv. which decreased significantly with hepatic anoxia or necrosis. Although the arrangement of liver cells does not suggest summation or synchronization of electrical activity, the active transport involved in bile formation does raise the possibility of a steady potential difference associated with biliary secretion. The present study was undertaken to measure the electrical changes in relation to biliary output under varying conditions. INVESTIGATION

METHODS

Six adult mongrel dogs weighing 8 to 10 kg. were lightly anesthetized with sodium F’rom the Department of Surgery, The Johns Hopkins University School of Medicine and The Johns Hopkins Hospital, Baltimore, Md. Submitted for publication Nov. 16, 1966. The Department of Surgery, * Current Address: George Washington University Hospital, Washington, D.C.

186

THE

CANINE

M.B., WALTER

F.

Report

LIVER

B.S.,* BALLINGER

II,

M.D.

pentothal; the common bile duct was exposed through a midline upper abdominal incision. A silver chloride electrode with a saturated KCl-3% agar bridge was introduced into the larger hepatic duct and gently pushed cephalad until the tip was well within the liver substance. A polythene tube of 0.2 mm. inside diameter was used to construct the bridge in all cases. A similar electrode was placed on the liver surface as the point of reference, and the 2 electrodes were connected to a Model 502A Tektronix dual beam oscilloscope. The potential difference with the tips of both bridges in saline was subtracted from all readings, and was generally 0 to 2 mv. Following the initial measurement, 100 ml. of 50% dextrose and 15 units of regular insulin were injected through a plastic cannula placed in a tributary of the portal vein, and measurements were repeated. The change in potential following the injection of 10 ml. of carbon tetrachloride was noted in all experiments. In all experiments, the lumen of the bile duct was found to be positive with reference to liver surface. Figure 1 represents the electrical potentials recorded in all the animals; The electrical potentials at the beginning of the experiments ranged from 3 to 15 mv. The infusion of a solution of dextrose and insulin was followed by a very brief fall in potential in 4 experiments (Numbers 2, 4, 5, and 6). The fall was slight in 3, but the fall was so marked in 1 of the animals that the potential

VALIATHAN

L.--l-+

I

5

IO

15

I

I

I

I

I

20 25 MINUTES

30

35

40

45

Changesin electrical potential of canine liver following intraportal infusion of dextrose and insulin, and carbon tetrachloride. Fig. 1.

changed to electro-negativity. Irrespective of a transient fall in potential or a stationary phase, all animals showed a marked increase in electrical potential following the infusion of dextrose and insulin after a latent period of approximately 10 minutes. The peaks varied from 10 to 40 mv. and declined over a period of 10 to 30 minutes. Administration of carbon tetrachloride caused a rapid fall in potential to levels equal to or lower than the corresponding initial values.

DISCUSSION In investigating the electrical activity of the liver, Beigelman et al. [l] employed microelectrodes to penetrate the tissues. In the present series of experiments, however, positive electrical potentials in the canine biliary tract were demonstrated with reference to the

ET

AL.:

ELECTRICAL

ACTIVITY

OF

THE

CANINE

LI\‘ER

liver capsule. In order to study the electrical response to metabolic changes, intraportal injection of dextrose and insulin, and carbon tetrachloride were employed because of their gluconeogenetic and hepatotoxic effects respectively. A consistent rise in potentials was observed following the administration of dextrose and insulin; a fall in potential followed a similar injection of carbon tetrachloride. Other preliminary observations suggest a quick and transient rise in potentials in response to the intraportal injection of 1 ml. of 1: 10,000 epinephrine, and a slow and gradual fall in potentials ranging from 1 to 3 mv. following the occlusion of the portal vein and hepatic artery. These electrical phenomena seem to resemble those observed in the salivary gland, and would appear to be connected with the functional work of liver cells.

SUMMARY In 6 experiments, the canine biliary tract was found to be electrically positive with reference to the liver capsule, and potentials ranging from 3 to 15 mv. were demonstrated. Intraportal infusion of a solution of dextrose and insulin caused a brief fall in potential in 4 of 6 experiments, followed by a sharp increase in all animals. Hepatic necrosis produced by carbon tetrachloride was associated with a marked fall in potential.

REFERENCE 1.

Beigelman, P. M., Coraboeuf, P. The electrical potential ( Oxford ) 3: 1343, 1964.

E., of

and liver.

Guibault, Life Sci.