Electrocardiac effects associated with lithium toxicity in children: an illustrative case and review of the pathophysiology

Lithium is a potent psychotherapeutic agent that has gained wide acceptance in paediatrics, especially as adjunct treatment for severe behavioural, anxiety, and attention-deficit hyperactivity disorders, along with bipolar conditions. Its cardiac toxicity has been well-documented in adults; however, information is limited regarding lithium’s effects on the heart in children. Therefore, paediatric cardiologists following-up children on lithium therapy should be cognizant of the cardiac side-effects and pathophysiology associated with this drug. In this manuscript, we used an illustrative case of a child who presented with lithium poisoning, in order to highlight adverse clinical manifestations that can arise from this medication. The cardiac cell membrane is thought to be the primary site of lithium’s action. Thus, we reviewed lithium’s effects on membrane electrogenic pumps and channels involved in the distribution and passage of sodium, potassium, and calcium across the sarcolemma, as these ions, and their associated currents, are the primary determinates of the action potentials underlying auto-rhythmicity and contractile activity of the heart.

Hydraulic and electrical transmission of wound-induced signals in Vitis vinifera

The nature and characteristics of the electrical response to wounding in the woody plant Vitis vinifera L. were examined. Following burning of a small area of a leaf, bioelectrical events spread throughout the shoot. The heat wound triggered stem deformations (widening–contraction), which preceded changes in biopotentials and that are interpreted as reflecting wound-induced hydraulic signals. It also caused marked decrease of extracellular resistance in stem tissues, starting about 15 s after stimulation, while intracellular resistance did not show any modification. Under an N2 atmosphere (hypoxic conditions), action potentials disappeared and the amplitude of variation potentials decreased approximately 50%. At saturating humidity variation potentials were completely eliminated, while action potentials were evident. Taken together, the results demonstrate that action and variation potentials differ both in their mechanism of propagation and electrogenic nature. Action potentials are ‘genuine’ self-propagating electrical signals travelling at a velocity of about 10 cm s-1, with a metabolic nature involving active components (electrogenic pumps). Variation potentials are a ‘local’ response to the passage of an hydraulic wave. Results support the hypothesis that both ion channels and pumps are involved in variation potential depolarisation.

Electrogenic pumps in higher plant cells

The evidence for the existence of electrogenic pumps in higher plant cells is reviewed. A new theory of electrogenic transport is given. Which ion is pumped and the energy source for electrogenic transport are discussed.

Ion transport and electrogenic pumps in storage tissue cells

Experimental evidence for the existence of electrogenic pumps in storage tissue cells is presented. The nature of the pump (which ion?, proton vs. bicarbonate transport, role of proton pump, K+–H+ exchange) is extensively discussed.