Comfrey herbal remedy causing second-degree heart block: do not be outfoxed by digitalis.

A previously well woman aged 63 years presents to the emergency department with vomiting, palpitations and 3 presyncopal episodes. She had no previous medical or cardiac history, with the patient stating that she tried a herbal remedy of boiled comfrey leaves for insomnia 18 hours before arrival to the department. Her ECG showed multiple abnormalities, including bradycardia, second-degree atrioventricular node block, Mobitz Type 2, a shortened QT interval, downsloping ST depression and presence of U waves. After viewing the images of comfrey and foxglove, it highlighted the possibility of mistaken ingestion of Digitalis, containing the organic forms of cardiac glycosides, such as digoxin and digitoxin. Raised serum digoxin levels confirmed this. The patient was haemodynamically stable, and given digoxin-binding antibodies. After 5 days of cardiac monitoring, her ECG returned to normal rhythm, and she was discharged home.

Digitalis purpurea P5 beta R2, encoding steroid 5 beta-reductase, is a novel defense-related gene involved in cardenolide biosynthesis.

The stereospecific 5 beta-reduction of progesterone is a required step for cardiac glycoside biosynthesis in foxglove plants. Recently, we have isolated the gene P5 beta R, and here we investigate the function and regulation of P5 beta R2, a new progesterone 5 beta-reductase gene from Digitalis purpurea. P5 beta R2 cDNA was isolated from a D. purpurea cDNA library and further characterized at the biochemical, structural and physiological levels. Like P5 beta R, P5 beta R2 catalyzes the 5 beta-reduction of the Delta(4) double bond of several steroids and is present in all plant organs. Under stress conditions or on treatment with chemical elicitors, P5 beta R expression does not vary, whereas P5 beta R2 is highly responsive. P5 beta R2 expression is regulated by ethylene and hydrogen peroxide. The correlation between P5 beta R2 expression and cardenolide formation demonstrates the key role of this gene in cardenolide biosynthesis, and therefore in the chemical defense of foxglove plants.

Effects of uremic serum on isolated cardiac myocyte calcium cycling and contractile function.

BACKGROUND: Diastolic dysfunction occurs in patients with chronic renal failure. Moreover, serum from uremic patients contains one or more inhibitors of the plasmalemmal Na,K-ATPase (sodium pump). We hypothesized that a circulating substance present in uremic sera contributes to both sodium pump inhibition and diastolic dysfunction. METHODS: Serum samples were obtained from six patients with chronic renal failure and diastolic dysfunction. RESULTS: Their serum samples caused marked inhibition of Na,K-ATPase purified from dog kidney at all concentrations studied (all P < 0.01) and also impaired ouabain-sensitive rubidium uptake by myocytes isolated from Sprague-Dawley rats (P < 0.01). These cardiac myocytes were studied for their contractile function with video-edge detection and calcium metabolism with indo-1 fluorescence spectroscopy after exposure to these uremic sera. These uremic sera caused increases in myocyte fractional shortening (P < 0.01) as well as an increase in the time constant of relengthening (P < 0.01). Examining the calcium transient, the time constant for calcium recovery was also increased (P < 0.01). Exposure of these cells to sera from age- and sex-matched healthy subjects did not result in significant changes in contraction or calcium cycling. Extracts of uremic serum samples inhibited isolated Na,K-ATPase whereas extracts of normal serum samples did not. The effect of uremic serum extracts on contractile function and calcium cycling were quite similar to that of intact serum or the addition of ouabain. Co-incubation of uremic serum extract with an antibody fragment directed against digoxin markedly attenuated the inhibition of Na,K-ATPase activity and completely prevented any effects on calcium cycling or contractile function. CONCLUSION: These data show that one or more substances are present in uremic sera that acutely cause increased force of contraction and impaired recovery of cardiac myocyte calcium concentration as well as impaired relaxation. As these effects are similar to that seen with ouabain and can be prevented by co-incubation with an antibody fragment to digitalis, which also attenuates the sodium pump inhibitory effect, we suggest that this (these) substance(s) circulating in uremic sera and inhibiting the sodium pump also causes the acute diastolic dysfunction seen in our system.

Treatment of a patient with severe digitoxin intoxication by Fab fragments of anti-digitalis antibodies.

A massive digitoxin (DGTX) intoxication in a 36-year-old man (35 mg DGTX) was treated by prolonged and repeated i.v.-infusions of Fab fragments of anti-digitalis antibodies (FAB). Blood and urine samples were collected over a 98 h period for monitoring the efficacy and adequacy of FAB treatment. DGTX concentrations were determined after protein precipitation (release of FAB-bound and protein-bound DGTX) in unprocessed serum and urine samples, and after aliquots of these samples had been dialysed in vitro against DGTX-free buffer (elimination of DGTX not bound to FAB). The difference in DGTX concentration between the unprocessed and dialysed samples was the amount of DGTX bound to plasma proteins and the small fraction of unbound DGTX being relevant for the therapeutic and toxic effects of the drug. Before FAB therapy was started, the total serum DGTX concentration was 535 nmol/l. The first FAB infusion (320 mg) was started 11 h after drug ingestion. Since this amount of FAB was insufficient to bind all DGTX present in the serum, cardiac DGTX toxicity (total AV-block) persisted. During a second FAB infusion (400 mg) the patient reverted to regular AV-conduction. At this time most of the DGTX in serum was FAB-bound. Toxic symptoms (sinus arrest) reappeared twice and were accompanied by increasing amounts of non-antibody-bound DGTX in the serum. Additional application of FAB (2 x 80 mg) resulted in the immediate disappearance of arrhythmia. During FAB-treatment total DGTX serum concentrations and renal DGTX clearance rose, indicating redistribution of drug from tissue to serum and urinary elimination of FAB-bound DGTX, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Preferential accumulation of radioactivity in rat kidneys after the administration of 125I-labelled Fab antidigitalis antibodies.

125I-labelled Fab antidigitalis antibodies were administered i.p. to rats, whose organs were removed 20 h later and examined for radioactivity. Maximum radioactivity was found in the thyroid region, followed by the kidneys, liver, adrenals, heart, skeletal muscle and brain. The radioactivity of kidneys was greater than in any of the other organs except the thyroid, where it probably resulted from the uptake of radioiodine, released from the antibodies. After injection of Na125I there was no difference between the kidneys and the liver. In kidney homogenates, radioactivity was present both in the 100,000xg pellet and in the supernatant. The possibility of accumulation or production of the endogenous digitalis-like factor in the kidneys is discussed.

[Treatment of severe digitoxin poisoning with digitalis antibodies]. / Behandlung einer schweren Digitoxinintoxikation mit Digitalis-Antikörpern.

In a 59-year-old patient who for suicide had taken 75 tablets of digitoxin the symptoms of a severe digitalis intoxication developed. By application of the digitalis antidote BM the life-threatening condition could quickly be mastered. Because of the distinct hyperkalaemia additionally an initial haemodialysis treatment was carried out.